Tetragonodon rex Kornicker & Harrison-Nelson 1999

Tetragonodon rex

ETYMOLOGY.—From the Latin rex (king).

HOLOTYPE.—MNHN-Os589, undissected adult female with large unextruded eggs, in alcohol.

TYPE LOCALITY.—Sta CPH04, East Atlantic, 20.334°N, 18.353°W, depth 2003 m.

PARATYPES.—Sta CPH04: USNM 194436A, adult female with unextruded eggs on slide and in alcohol; USNM 194436B, partly dissected ovigerous female; USNM 194436D, partly dissected A–1 male. Sta KGS46: USNM 194443A, ovigerous female; USNM 194443B, adult male on slide and in alcohol; USNM 194443D, instar I on slide and in alcohol; USNM 194443E, instar II on slide and in alcohol; USNM 194443F, G, 2 instar III females on slides and in alcohol; USNM 194443H, instar III female; USNM 194443K, instar III male in alcohol; USNM 194443C, instar IV male on slide and in alcohol; USNM 194443J, instar IV male; USNM 194443L, partly dissected instar II; USNM 194443M, instar III female; USNM 194443N, instar III female; USNM 194443P, instar III female; USNM 194443Q, instar III female; USNM 194443R, instar III female; USNM 194443S, instar III male; USNM 194443T, partly dissected instar III male on slide and in alcohol; USNM 194443U, instar III female; USNM 194443V, instar III female; USNM 194443W, instar IV male; USNM 194443X, instar IV male; USNM 194443Y, instar IV female; USNM 194443Z, instar IV male; USNM 194443A A, partly dissected instar IV female; USNM 194443AB, adult female with unextruded eggs; USNM 194443AC, instar IV male (shell distorted).

DISTRIBUTION.—Sta CPH04, 2003 m, KGS46, 1789 m.

DESCRIPTION OF ADULT FEMALE (Figures 2–4, 23a).—Carapace elongate with prominent rostrum and caudal process (Figures 2a, 23a); rostrum with lateral overlap along anterior and ventral margins and with pointed tip (Figures 2, 23a); hinge long and straight when viewed from inside.

Carapace Size (length, height in mm): Sta CPH04: USNM 194436A, 2.07, 1.28; USNM 194436B, 1.94, 1.18; Holotype, MNHN-Os589, 2.08, 1.29. Sta KGS46: USNM 194443A, 2.09, 1.42; USNM 194443AB, 2.07, 1.22.

Ornamentation: Rostrum with 3 small indistinct processes along the ventral margin (Figure 2b,d) and 3 or 4 fairly stout spines near tip (Figure 2d,e). Surface with many long bristles (Figure 2b,d,e) of which few in posterior half of valve are bifurcated, and with abundant shallow fossae (fossae represented by crescents in Figure 2b).

Infold: Rostral infold with 4 hirsute bristles and 2 short bristles at inner end of incisur (Figure 2c); infold ventral to incisur with short bristle; anteroventral infold and anterior half of ventral infold with about 6 narrow ridges paralleling valve margin, but without bristles. List of caudal process with row of 6 flat spinous bristles; inner edge of infold anterior to caudal process with 3 small bristles; posterior edge of caudal process with 3 small bristles.

Selvage: Wide fringed lamellar prolongation present along valve margin except along hinge and posterior edge of caudal process; prolongation divided at inner end of incisur.

Central Adductor Muscle Attachments: Numerous ovoid attachments.

First Antenna (Figure 3a,b): 1st joint with few indistinct distal dorsal spines. 2nd joint with few medial, lateral, ventral, and dorsal spines, and 1 dorsal bristle with long proximal spines. 3rd joint short, with medial spines near ventral margin, and 3 bristles (2 dorsal, 1 ventral) with long proximal spines. 4th joint long with medial spines near ventral margin and 2 or 3 subterminal spinous bristles (1 ventral, 1 or 2 dorsal). Sensory bristle of long 5th joint with 3 short proximal filaments and 4 terminal filaments. 6th joint short, fused to 5th joint, with short spinous medial bristle. 7th joint: a-bristle longer than bristle of 6th joint, with long spines; b-bristle shorter than sensory bristle, with 1 short proximal filament and 3 short terminal filaments; c-bristle almost as long as sensory bristle, with 2 proximal and 4 terminal filaments. 8th joint: d- and e-bristles as long as c-bristle, bare with blunt tips; f-bristle about same length as c-bristle, with 2 proximal and 4 terminal filaments; g-bristle as long as sensory bristle, with 2 proximal and 4 terminal filaments.

Second Antenna: Protopodite bare, without e-sclerite (Figure 3c). Endopodite 2-jointed (Figure 3c,d): 1st joint with short bristle; 2nd joint with long subterminal (Figure 3c) or terminal (Figure 3d) bristle with long spines. Exopodite: 1st joint with minute curved terminal medial tubular bristle (Figure 3e); bristle of 2nd joint reaching past 9th joint, bare; bristles of joints 3–8 slightly longer, bare except for few indistinct hairs at tip; 9th joint with 3 bristles (1 short (dorsal), 1 medium, 1 about same length as bristle of 8th joint), all bare except for few indistinct hairs at tip; joints 2–8 with short spines forming rows along distal edges.

Mandible (Figure 3f): Coxale endite spinous, tip bifurcate, without bristle near base. Basale: dorsal margin with 3 bristles (1 distal to midlength, 2 terminal); ventral margin with 1 spinous subterminal bristle; medial surface spinous, with 5 short spinous bristles near ventral margin (4 proximal, 1 distal); lateral surface with 4 bristles with bases on or near ventral margin. Exopodite spinous, about to length of dorsal margin of 1st endopodial joint, with 2 spinous subterminal bristles. 1st endopodial joint: medial surface and distal dorsal margin spinous; ventral margin with 3 bristles (1 short with short spines, 2 long with long and short spines). 2nd endopodial joint: medial surface, ventral margin, and proximal dorsal margin spinous; ventral margin with 3 or 4 spinous bristles forming 2 groups (1 or 2 in proximal group, 2 in distal group); dorsal margin with spinous bristles forming 2 groups with 2 bristles in proximal group and 5 in distal group. 3rd endopodial joint with 3 claws (dorsal claw small with few indistinct proximal teeth, 2 long claws bare) and 3 slender ringed bristles. (Rings not shown on all ringed bristles.)

Maxilla (Figure 3g,h): Precoxale with fringe of dorsal hairs. Coxale with stout spinous dorsal bristle. Endites I and II each with 6 spinous and pectinate bristles; endite III with 1 proximal and 7 distal spinous bristles. Basale with 3 spinous bristles (2 ventral, 1 dorsal). Exopodite with 3 spinous bristles (2 long, 1 short). 1st endopodial joint with 1 alpha-bristle, 2 spinous beta-bristles, and node medial to longer beta-bristle. 2nd endopodial joint with dorsal spines, 3 long spinous a-bristles, 4 spinous ringed bristles, and 3 stout claws.

Fifth Limb (Figure 4a–c): Endite I with 2 bristles (not shown); endite II with 5 or 6 bristles (not shown); endite III with 10 spinous and pectinate bristles (Figure 4b). 1st exopodial joint: main tooth with short proximal bristle, 1 slender pointed tooth, stout pointed tooth with 2 long subterminal cusps, and 2 stout blunt teeth (tips broken off?) (Figure 4c); anterior side with 2 spinous bristles (Figure 4b); outer edge with small lobe with short spinous bristle (Figure 4a,b). 2nd exopodial joint with large square tooth with 3 bristles, possibly 4 (bristles obscured on mounted limbs), near inner edge (Figure 4a). 3rd exopodial joint with 3 bristles on inner lobe and 2 spinous outer bristles (outer lobe not developed) (Figure 4a). 4th and 5th exopodial joints fused, hirsute, with total of 5 spinous bristles (Figure 4a).

Sixth Limb (Figure 4d): Epipodite with 1 spinous bristle. Endite I with 3 short bristles; endite II with 3 or 4 spinous terminal bristles; endite III broad with 7 spinous bristles; endite IV broad with 5 spinous bristles. End joint with 5 bristles with long proximal and short distal spines followed by 2 hirsute bristles. (Many bristles broken off on illustrated limb.)

Seventh Limb (Figure 4e,f): 4 bristles in proximal group (2 on each side), each with 3 or 4 bells and marginal spines; 6 bristles in terminal group (3 on each side), 2 with 2 bells, 4 with 5 or 6 bells, all with marginal spines. Terminus with comb of 8 alate teeth opposite 4 small pegs (Figure 4f). Marginal spines of bristles consist of 1 group near midlength and 1 distal.

Furca: Each lamella with 9 articulated claws decreasing in length and width along lamella. Medial side of claw 1 with long distal tooth and shorter teeth proximally. Right lamella anterior to left by width of claw 1.

Bellonci Organ and Eyes: Absent.

Upper Lip: Hirsute, with anterior projection bearing 3 small tubular processes at tip.

Genitalia (Figure 4h): Sclerotized oval on each side of body anterior to furca.

Brush-like Organ (Figure 4h): Six slender minute bristles attached to genitalia.

Y-Sclerite (Figure 4h): Without ventral branch.

Number and Size of Eggs: USNM 194436B with 6 eggs in marsupium; length of typical egg 0.40 mm. USNM 194443A with 5 eggs in marsupium; length of typical egg 0.47 mm. Both specimens without unextruded eggs in ovaries.

Epizoa (Figure 2a): USNM 194436A and USNM 194443A with stalked hydroids attached to carapace near anterodorsal margin.

Gut Content: All specimens contained unidentified brown particulate matter in the gut. After dissection the slide with USNM 194436A contained a whole rotaloid foraminiferan shell, and the slide of USNM 194436B contained a Y-shaped spicule, but it is not certain they were from the gut.

DESCRIPTION OF ADULT MALE (Figures 5–7).—Carapace shape, infold, and central adductor muscle attachments similar to those of adult female. Tip of rostrum may be slightly more rounded, and extent of anterior overlap of tip of rostrum may be slightly less than on adult female (Figure 5a,d).

Ornamentation: Surface of rostrum with fewer processes along ventral margin than on adult female (Figure 5a); surface of caudal process with some bristles longer than those of adult female (Figure 5c). Bifurcate bristle present near posteroventral edge of left valve of USNM 194443B (Figure 5b); some short bristles with tips somewhat drawn-out (whip-like) (Figure 5b).

Carapace Size (length, height in mm): USNM 194443B (distorted carapace): right valve 1.89, 1.36; left valve, length only 2.00.

First Antenna (Figure 5e,f): 1st joint bare. 2nd joint with row of short distal lateral spines, abundant long medial hairs, and 1 spinous dorsal bristle. 3rd joint short with rows of medial spines near dorsal margin, and 3 bristles (2 dorsal, 1 ventral). 4th joint long, with 3 bristles (1 dorsal, 2 ventral). 5th joint wedged ventrally between 4th and 6th joints; sensory bristle with stout cup-like proximal part with abundant slender filaments, and long stem with 2 or 3 marginal filaments and bifurcate tip. 6th joint long with medial terminal bristle with long proximal and short distal spines. 7th joint: a-bristle slightly longer than bristle of 6th joint, with either long proximal and short distal marginal spines, or only short spines; b-bristle about twice length of a-bristle, with 3 short marginal filaments and bifurcate tip; c-bristle very long with 11 marginal filaments and bifurcate tip. 8th joint: d- and e-bristles almost twice length of b-bristle, bare with blunt tips; f-bristle very long with 8 marginal filaments and bifurcate tip; g-bristle slightly longer than e-bristle, with about 9 marginal filaments and bifurcate tip. (Left limb of USNM 194443B aberrant in having only 1 dorsal bristle on 3rd joint, 1 ventral bristle on 4th joint, and an unextruded c-bristle of 7th joint visible within limb.)

Second Antenna: Protopodite with e-sclerite (Figure 6a). Endopodite 3-jointed (Figure 6a,b): short 1st joint with 4 short bristles (3 in row, 1 more distal); long 2nd joint with 2 long slender bristles either bare or with short indistinct marginal spines; reflexed long 3rd joint with 2 small subterminal bristles and sclerotized pointed tip. Exopodite: long 1st joint with minute medial terminal tubular bristle; 2nd joint only slightly longer than 3rd joint; bristles of joints 2–8 long with natatory hairs, no spines; 9th joint with 3 bristles (2 long with natatory hairs, and 1 short (dorsal) either bare or with few indistinct spines) (Figure 6c); joints 3–9 with small spines forming distal lateral row.

Mandible (Figures 6d, 7a): Coxale with 2 minute medial spines near distal ventral corner. Basale: medal surface spinous, with 4 small proximal bristles on ridge near ventral margin (Figure 7a), 1 short spinous bristle near midlength, and 1 long subterminal bristle with base almost on ventral margin; ventral margin with 4 long ventral bristles; dorsal margin spinous, with 1 bristle at distal and 1 subterminal. Exopodite about length of dorsal margin of 1st endopodial joint, with distal hirsute pad and 2 subterminal bristles of similar length. 1st endopodial joint with medial spines and 3 ventral bristles. 2nd endopodial joint with medial and ventral spines; ventral margin with 2 pairs of distal spinous bristles; dorsal margin with 7 bristles (2 at proximal , 5 at midlength). 3rd endopodial joint with 3 claws (dorsal claw short) and 3 short ringed bristles. (The right limb of USNM 194443B has only 2 separated ventral bristles on the 2nd endopodial joint and is missing 1 long and 1 short claw on the 3rd joint; whether the limb is aberrant or if the bristles and claws were lost during dissection is not known.)

Maxilla: Limb reduced. Precoxale, coxale, and basale with dorsal hairs. Coxale with plumose dorsal bristle (Figure 6e,f). Endites I and II each with 5 weak bristles; endite III with 7 weak distal bristles (Figure 6g). Basale with 1 or 2 distal bristles (Figure 6e). Exopodite well developed, with 1 short and 2 long bristles. 1st endopodial joint with 1 alpha- and 2 beta-bristles. 2nd endopodial joint with 11 weak bristles.

Fifth Limb (Figure 7b): Limb weakly developed. Endites I and II each with 1 short bristle. Endite III with 7 small weakly developed bristles. Exopodite: 1st joint with 5 small bristles (3 finger-like); 2nd joint with 5 finger-like bristles (terminal bristle stouter than others). 3rd exopodial joint: inner lobe with 3 bristles (1 long ringed spinous); outer lobe with 2 ringed spinous bristles. 4th and 5th exopodial joints fused, hirsute, with 4 or 5 ringed spinous terminal bristles. Epipodite with 49 plumose bristles.

Sixth Limb (Figure 7c): Limb hirsute. Epipodite with 1 spinous bristle. Endite I small with 2 or 3 small bristles; endite II narrow, with 3 spinous terminal bristles; endite III wider than endite II, with 7 spinous terminal bristles; endite IV longer but about same width as endite II, with 5 spinous terminal bristles. End joint with 5 or 6 spinous bristles followed by 2 stouter plumose bristles. All bristles ringed (rings not shown).

Seventh Limb (Figure 7d): Proximal group with 3 bristles (2 on one side, 1 on other side), each with spines and 3 or 4 bells. Terminal group with 4 bristles (2 on each side), each with spines and 5 or 6 bells. Terminus consisting of comb with 8 alate teeth opposite 2 slender pegs.

Furca (Figure 5g): USNM 194443B with 8 claws on right lamella and 9 on left; furca similar to that of female except without stout medial teeth on claw 1.

Bellonci Organ and Eyes: Absent.

Upper Lip (Figure 7e): Hirsute, with anterior projection.

Genitalia (Figure 7f): Each copulatory organ with terminal hook-like process with bifurcate tip and several small bristles.

Posterior of Body: With few rows of minute indistinct spines anterior to dorsal end of girdle.

Y-Sclerite: Left sclerite of USNM 194443B with minute ventral branch (Figure 7g (left)); right sclerite without ventral branch (Figure 7g (right)).

Gut Content: The single adult male specimen in the collection contained unidentified amber-colored particulate matter in the gut; the particles did not appear to be much different than those observed in adult females and juveniles, but observations of gut content were mostly made through the integument of the body, rather than emptying the gut.


DESCRIPTION OF INSTAR I (sex unknown) (Figures 8–11).—Carapace shape (Figure 8a), ornamentation (Figure 8b,c), and central adductor muscle scars (Figure 8a), in general, similar to those of adult female. (USNM 194443D with valves and appendages of instar II visible within those of instar I.)

Infold: Rostral infold (Figure 8d), anteroventral infold, and anterior half of ventral infold similar to those of adult female; infold of caudal process with 1 flat spinous bristle along anterior ridge (Figure 8e); 3 small bristles along posterior edge of caudal process; ventral infold just anterior to caudal process with 1 or 2 small bristles.

Carapace Size (length, height in mm): USNM 194443D, 0.95, 0.59 (instar II appendages visible inside appendages of instar I).

First Antenna (Figure 8f): 1st joint with few short medial spines. 2nd joint with lateral, ventral, and dorsal spines. 3rd joint short with 2 spinous bristles (1 ventral, 1 dorsal). 4th joint with rows of long distal lateral, medial, ventral, and dorsal spines. Sensory bristle of long 5th joint bare except for terminal papilla. 6th joint short, fused to 5th joint, with short spinous medial bristle. 7th joint: a-bristle longer than bristle of 6th joint, with long proximal spines; b-bristle shorter than sensory bristle, bare except for terminal papilla; c-bristle almost as long as sensory bristle, bare except for terminal papilla. 8th joint: d- and e-bristles almost as long as sensory bristle, bare with broadly rounded blunt tips; f-bristle longer than b-bristle but shorter than c-bristle, bare except for terminal papilla; g-bristle about same length as sensory bristle, bare except for terminal papilla.

Second Antenna: Protopodite bare, without e-sclerite (Figure 9a). Endopodite 2-jointed or weakly 3-jointed (Figures 9a, 11c): 1st joint bare; 2nd joint (or fused 2nd and 3rd joints) with long spinous bristle and short terminal bristle. Exopodite: 1st joint with minute oblique terminal medial bristle with tubular tip (Figure 9c); bristle of 2nd joint reaching well past 9th joint, bare; bristles of joints 3–8 slightly longer, bare; 9th joint with 2 bare bristles (1 short (dorsal), 1 medium not reaching past tips of bristles of joints 3–8) (Figure 9b); joints 3–8 with row of long spines along distal edges.

Mandible (Figure 9d): Coxale endite similar to that of adult female. Basale: dorsal margin with 2 or 3 bristles (1 distal to midlength, 1 or 2 subterminal, bare or with short spines); ventral margin spinous; medial surface spinous with 5 short spinous bristles near ventral margin (4 proximal, 1 near midlength). Exopodite similar to that of adult female. 1st endopodial joint: medial surface and distal dorsal margin with spines; ventral margin with 2 long bristles with long and short spines. 2nd endopodial joint: medial surface and ventral margin spinous; ventral margin with 1 short distal spinous bristle; dorsal margin with 4 or 5 spinous bristles. 3rd endopodial joint with 2 stout unringed claws with proximal ventral teeth, and 2 slender ringed bristles (1 dorsal, 1 ventral). (Short dorsal claw present on adult 3rd joint absent on instar I.)

Maxilla: Precoxale and coxale with dorsal hairs. Coxale with plumose dorsal bristle (Figure 9e). Endite I with 6 spinous bristles (Figure 9e); endites II and III each with 4 spinous bristles. Basale with 2 spinous ventral bristles (1 medial, 1 lateral) (Figure 9e,f). Exopodite similar to that of adult female (Figure 9f). 1st endopodial joint with 1 alpha-bristle and 1 spinous beta-bristle, and node medial to beta-bristle (Figure 9g). 2nd endopodial joint with 2 long spinous a-bristles, 2 spinous ringed bristles, and 1 stout claw (Figure 9g).

Fifth Limb: Epipodite with 38 hirsute bristles. Endite I with 1 spinous bristle; endite II with 3 spinous bristles and 1 short broad triangular process with slender prolonged tip; endite III with 4 spinous or pectinate bristles and 1 short broad triangular process with slender prolonged tip (Figure 10a). 1st exopodial joint represented by stout peg-like anterior tooth projecting from 2nd joint (Figure 10a,b), and by curved sclerotized posterior ridge (Figure 10b,c). 2nd exopodial joint a broad stout flat tooth with small posterior bristle near outer edge (Figure 10c). 3rd exopodial joint: inner lobe represented by 2 slender bristles (lobate structure absent) (Figure 10a,c); outer lobe either absent or represented by 1 bristle (bristle could be interpreted to be on either 1st or 2nd exopodial joint). 4th and 5th exopodial joints fused, hirsute, with 2 stout spinous bristles (Figure 10c). Two additional spinous exopodial bristles present belong to either the 1st or 2nd exopodial joints (Figure 10c). (The complex tooth of the 1st exopodial joint of the 5th limb of instar II is visible (stippled) inside the 2nd exopodial joint of the 5th limb of instar I of USNM 194443D (Figure 10d).)

Sixth Limb (Figure 11a): With abundant slender spines but no bristles.

Seventh Limb: Absent.

Furca (Figure 11b,d): Each lamella with 3 articulated claws; claw 3 much shorter than claws 1 and 2. Medial side of claw 1 with large slender distal tooth and shorter teeth proximally; posterior edge with row of short, slender teeth distal to long medial tooth. Claw 2 with slender teeth along posterior edge and long slender tooth just proximal to midlength. Claw 3 with small proximal posterior node. Right lamella anterior to left by width of claw 1. Anterior and ventral edges of each lamella spinous. (The furca of instar II, with 5 or 6 slender claws, is visible inside the furca of instar 1 of USNM 194443D (Figure 11d).)

Bellonci Organ, Eyes, and Genitalia: Absent.

Posterior of Body (Figure 11e): With few rows of small spines on posterodorsal corner.

Y-Sclerite (Figure 11e): Appears fused to ventral end of girdle.

Gut Content: Unidentified brown particulate matter. (Although USNM 194443D was in an advanced state of ecdysis, having appendages of instar II visible within the appendages, the gut was full.)

DESCRIPTION OF INSTAR II ?MALE (Figures 12–14a–j).—Carapace shape (Figure 12a), ornamentation (Figure 12b,c), and central adductor muscle attachments (Figure 12a), in general, similar to those of adult female. USNM 194443E with small process with terminal spine (similar to type on rostrum) on anteroventral edge of valve (Figure 12a).

Infold: Rostral, anteroventral, and anterior half of ventral infold similar to those of adult female (Figure 12d). Infold of caudal process with 3 flat spinous bristles along anterior ridge (Figure 12e); outer edge of caudal process with 3 minute bristles; ventral infold just anterior to caudal process with 1 or 2 small bristles.

Carapace Size (length, height in mm): USNM 194443E, 1.09, 0.64 (instar III appendages visible within appendages of instar II).

First Antenna (Figure 12f): 1st joint with few short lateral spines. 2nd joint with lateral and dorsal spines and spinous dorsal bristle. 3rd joint short with 2 spinous bristles (1 ventral, 1 dorsal). 4th joint with spinous dorsal bristle. Sensory bristle of long 5th joint with 1 proximal and 2 terminal filaments. 6th joint short, fused to 5th joint, with short spinous medial bristle. 7th joint: a-bristle longer than bristle of 6th joint, with long proximal spines; b-bristle shorter than sensory bristle, with 1 short distal filament; c-bristle only slightly shorter than sensory bristle, with 2 terminal filaments. 8th joint: d- and e-bristles as long as sensory bristle, bare with blunt tips; f-bristle about same length as c-bristle, with 1 proximal and 2 terminal filaments; g-bristle as long as sensory bristle, with 1 proximal and 2 terminal filaments.

Second Antenna: Protopodite bare without e-sclerite (Figure 12g). Endopodite 2-jointed (Figure 12g,h): 1st joint with short bristle; 2nd joint elongate with spinous bristle near midlength. Exopodite: similar to that of instar I except 9th joint with 3 bristles (1 short (dorsal), 1 medium, 1 about same length as bristle of 8th joint) (Figure 12i); joints 2–8 with short spines along distal edge.

Mandible (Figure 13a): Coxale endite similar to that of adult female. Basale: dorsal margin with 3 bristles (1 distal to midlength, 2 terminal); ventral margin spinous; medial surface spinous, with 5 bristles near ventral margin (4 proximal and 1 near midlength); lateral surface spinous, with none or 1 bristle near ventral margin at midlength. 1st endopodial joint: medial surface and distal dorsal margin with spines; ventral margin with 3 bristles (1 short with few spines, 2 long with long spines). 2nd endopodial joint: medial surface, ventral margin, and proximal dorsal margin spinous; ventral margin with 3 short spinous bristles forming 2 groups (1 in proximal group, 2 in distal group); dorsal margin with 6 bristles. 3rd endopodial joint with 3 claws (dorsal claw small; 2 long claws with proximal ventral teeth) and 3 slender ringed bristles (2 ventral, 1 near dorsal edge).

Maxilla: Coxale with stout plumose dorsal bristle (only proximal end shown in Figure 13b). Endite I with 5 spinous bristles (Figure 13b); endites II and III each with 6 spinous bristles (Figure 13c). Basale with 3 spinous bristles (2 ventral, 1 dorsal (this bristle could be interpreted to be on endite III)) (Figure 13b). Exopodite similar to that of adult female (Figure 13f). 1st endopodial joint spinous, with 1 spinous alpha-bristle, 2 spinous beta-bristles, and node medial to base of outer beta-bristle (Figure 13b,d). 2nd endopodial joint with 3 spinous a-bristles, 2 slender bristles (longer ringed), and 3 stout bare claws (Figure 13e,f).

Fifth Limb: Epipodite with about 45 bristles (a few may be missing from mounted limb). Endite I with 2 bristles; endite II with 5 bristles; endite III with about 8 bristles (Figure 13g,h). 1st exopodial joint: main tooth with short proximal bristle and 3 pectinate teeth (Figure 13g,i); anterior side with 2 bristles (not shown). 2nd exopodial joint with large square tooth with 4 posterior bristles (1 long proximal and row of 3 slightly distal (1 short bristle on each side of 1 long bristle (Figure 13i)). 3rd endopodial joint with 2 bristles on each lobe. 4th and 5th exopodial joints fused, with total of 5 spinous bristles (Figure 13g).

Sixth Limb (Figure 14a–d): Single endite with 1 spinous bristle and long spines; remainder of limb undulate and with long spines.

Seventh Limb (Figure 14e,f): Short, thumb-like, bare.

Furca (Figure 14i): Each lamella with 6 pectinate articulated claws; claws 1 and 2 with long slender medial tooth near midlength. (Furca of USNM 194443E lost after drawing.)

Bellonci Organ (Figure 14g,h): Small, elongate, with tapered tip on USNM 194443E.

Eyes: Lateral eyes absent. Small ovoid process at base of Bellonci organ may represent medial eye, but without internal structures usually present in medial eyes.

Genitalia: Absent.

Posterior of Body (Figure 14j): Bare.

Y-Sclerite (Figure 14j): Unbranched and not fused to girdle.

Gut Content: Gut full of amber-colored particulate matter.

Remarks (Figure 14c,d): In USNM 194443E (instar II) the appendages of the next instar (instar III) are indistinctly visible within the appendages. Examination of the 6th limb suggests that the single endite of instar II has within it endites I–III of instar III, and the posterior lamellar-like part of instar II has within it both endite IV and the end joint of instar III. The bristle on the single endite of instar II appears to be equivalent to a bristle on endite III of instar III. Poulsen (1962:74–75, fig. 36f) observed that the 2nd larval stage of a specimen of Gigantocypris muelleri Skogsberg, 1920, seemed to have within its single endite three endites of the following stage. The spines along the edges of the limb of instar II of T. rex are not incipient bristles; spines also are present along the edges of the internal limb of instar III.

USNM 194443E is interpreted to be a questionable male because of the proximal location of the long bristle on the 2nd endopodial joint of the 2nd antenna.

DESCRIPTION OF INSTAR II ?FEMALE (Figure 14k,l).—Carapace shape, ornamentation, and central adductor muscle scars similar to those of instar II ?male, except without small anteroventral process present on USNM 194443E.

Carapace Size (length, height in mm): USNM 194443L, 1.21, 0.72 (instar III appendages visible within appendages of instar II).

First Antenna: Similar to that of instar II ?male.

Second Antenna: Protopodite and exopodite similar to that of instar II ?male. Endopodite 2-jointed (Figure 14k): 1st joint with short bristle; 2nd joint shorter than that of instar II ?male, and with long terminal bristle.

Mandible, Maxilla, Fifth Limb: Not examined in detail but, in general, similar to those of instar II ?male.

Sixth Limb, Seventh Limb (Figure 14l), and Y-Sclerite: Similar to those of instar II ?male. (Figure 14l shows 7th limb of instar III (stippled) within 7th limb of instar II.)

Furca: Furca of USNM 194443L with 8 claws of instar III indistinctly visible within 6-clawed furca of instar II. Right lamella of USNM 194443L aberrant in having 4th claw about length of 5th claw.

Bellonci Organ: Absent on USNM 194443L.

Genitalia: Absent.

Posterior of Body: With spines dorsal to dorsal end of girdle.

Gut Content: Gut full of unidentified amber-colored particulate matter.