“Isophryxus concavus n. sp.
Figs. 17A-171, 18A-18H, 180, and 18P
Description. Cephalon and three peraeonal segments indicated in dorsal view; pleon obscured, but somewhat triangular in outline. Body modified like suction cup (ventral view) for attachment to host. Peraeonal segments I–III with lateral edges projecting beyond hooded frontal body margin; edges of peraeonal segment IV indicated posterior to edges of segments I–III. Antennae absent. Buccal mass flattened, set deeply within flange-like frontal margin. Five pairs of short prehensile peraeopods present. Small oostegites developed on anterior segments, forming part of brood chamber set between short peraeopods. Large posterior oostegites enclose brood chamber. Medial ventral seam between oostegites extends caudally, forming a hole (just anterior to pleon), cut off by deep lateral sutures. Some mouth parts distinct, but most not immediately apparent as mouth parts (see Figures 18C-18G). Host unknown.
Male. (Enclosed in brood chamber of female.) Blind; 2.6 mm long. About one third as wide as long. Cephalon and first peraeonal segment fused; peraeon with five anterior segments about as wide as widest part of fused cephalon and peraeonal segment I; segment VII narrow; pleon with all segments fused, triangular and longer than broad. Evenly rounded lateral borders on peraeonal segments, and rounded posterior margin on pleon. No pleopods present. Peraeopods (seven pairs) prehensile; peraeopod I slightly smaller than peraeopod VII. Antenna 1 very short with conicular segments; segment 3 with single aesthetasc. Antenna 2 with broad irregularly shaped peduncular segment 1; next two segments subequal; apical segment small, tipped with several setae. The species name concavus, from the Latin, simply means that the general body form is concave or with a suction cup–like ventral surface.
Measurements. Holotype female, 21.6 mm long; allotype male, 2.6 mm long.
Type locality. 19-1480: 47°14'S, 132°28'W; 47°08'S, 132°43'W; 329 m. Holotype female; allotype male.
Distribution and size. 11-888 (one female, 14.5 mm); 11-919 (one female, 12.4 mm; one male, 2.b mm); 15-1294 (one female, 13.5 mm); 15-1302 (one female, 11 mm); 15-1320 (one female, 20 mm; one male, 3.4 mm); 19-1462 (one female, 8.5 mm); 19-1480 (one female, 21.6 mm; one male, 2.6 mm).
Affinities. The species differs from Holophryxus alascensis Richardson [1905b1 because peraeonal segments are indicated in the dorsal view. The species differs from Colophryxus novangliae Richardson [19081 because the new species lacks two laterally placed brood sacs. Richardson 11905a, p. 5751 discusses various genera related to the new genus.”
(Schultz, George, 1977: 93-96)
