Calathaemon holthuisi (Strenth 1976)

Palaemonetes holthuisi

DISPOSITION OF TYPES.—Male holotype, USNM 152391, and paratype USNM 152392; one male paratype, Rijksmuseum van Natuurlijke Historic Leiden, The Netherlands.

TYPE-LOCALITY.—Subterranean waters of Ezell’s Cave in the city of San Marcos, Hays County, Texas.

DESCRIPTION.—Rostrum (Figure 1a) high, compressed and short, reaching only to distal margin of basal segment of antennular peduncle; upper margin bearing four to eight teeth, one or two placed behind orbit; lower rostral margin devoid of teeth and distally with only few setae. Antennal spine slender and distinct, its base removed short distance from anterior margin of carapace. Branchiostegal spine situated somewhat ventral to branchiostegal groove and removed short distance from anterior margin of carapace.

Pleura of fourth and fifth abdominal somites forming acute to right angle; sixth somite twice as long as fifth. Telson (Figure 1b) atypical; posterior margin widened with six to ten small spines and one enlarged lateral pair placed just mesial to lateralmost smaller pair; two pair of dorsal spines placed along lateral margins.

Eyes (Figure 1a) reduced, without pigment, and bullet shaped in appearance; cornea completely degenerated.

Stylocerite (Figure 1e) of antennular peduncle sharp at tip; upper antennular flagellum with rami united for only five to six articles; free portion of shorter ramus consisting of 19 to 20 articles.

Scaphocerite (Figure 1d) almost twice as long as wide, lateral margin straight; blade extending beyond lateral tooth; antennal flagellum exceeding 250 mm in length.

Mandible (Figure 1f) with molar process typical, incisor process reduced to a short triangular structure. Maxillula (Figure 1g) with mesial lacinia greatly enlarged; median lacinia rather slender. Maxilla (Figure 1h) typical in size and shape. First maxilliped (Figure 1i) somewhat elongated with enlarged cup-shaped endites hooding greatly enlarged mesial lacinia of maxillula. Second maxilliped (Figure 1j) greatly enlarged due to elongation of virtually all segments, most notable in the distal ones. Third maxilliped (Figure 1k) typical, extending anteriorly just past end of antennal peduncle.

First pereiopod (Figure 1l) extending to distal margin of scaphocerite; palm and finger bearing numerous setae distally; carpus 2.5 times as long as chela and subequal in length to merus. Second pereiopod (Figure 1m) similar in length of first pereiopod; carpus 2.5 times as long as chela, merus twice as long as chela. Third pereiopod (Figure 1n) overreaching scaphocerite by half length of propodus; propodus and merus of equal length with carpus only five-sixths length of propodus. Fourth and fifth pereiopods similar to third.

Appendix masculina (Figure 1c) of male with nine apical spines. Lateral ramus of uropod (Figure 1b) without movable spine between fixed distolateral tooth and margin of blade.

SIZE.—Males with carapace length to 6 mm (including rostrum, to 8 mm).

VARIATION.—This species like Palaemonetes tonkinensis (Sollaud, 1914) bears a telson, which is atypical for the genus. The telson does resemble that of larval palaemonids as noted by Holthuis (1952:206) and is possibly of neotenic origin.

RANGE.—This species is known only from Ezell’s Cave in the city of San Marcos, Hays County, Texas.