Ascorhynchus prosus Nakamura, K. & C. A. Child 1983

Ascorhynchus prosum

MATERIAL EXAMINED.—Sagami Bay: Off Shimoda, 18 Aug 1973 (1, holotype, USNM 183807, 1, allotype, USNM 183808).

DESCRIPTION OF HOLOTYPE.—Moderately small, leg span about 24 mm. Trunk elongate, fully segmented, with median dorsal trunk tubercles, each slightly longer than its diameter. Anterior of cephalic segment without tubercles over chelifore insertion. Lateral processes separated by about their diameters, from 1 to 1.5 times longer than their diameters, armed with dorsodistal tubercles slightly shorter than median trunk tubercles. First, second, and fourth lateral processes armed with a posterolateral seta, second and third lateral processes with an anterolateral seta or spine near base of process. Ocular tubercle placed above palp bases, at extreme anterior of cephalic segment, more than twice as tall as its median diameter, projecting anteriorly. Eyes small, lightly pigmented, placed distally on ocular tubercle just below apical cone. Proboscis long, almost 0.6 of trunk length, with distal and proximal constrictions giving trilobed shape, oral surface flat, lips flat. Abdomen long, reaching almost to tips of second coxae on fourth legs, slightly swollen distally, armed with several dorsodistal setae.

Chelifore scape 1-segmented, short, swollen, armed with several ventral and distal setae. Chela tiny, globular, fingers represented by anterior cleft.

Palp 10-segmented, basal 2 segments small, not longer than wide, third segment longest, slightly longer than fifth. Fifth segment armed with several dorsal and lateral setae, 1 long endal seta. Terminal 5 segments increasingly shorter, each only slightly longer than its diameter, armed with many ventral setae, some longer than segment diameter.

Oviger 10-segmented, implanted just anterior to and not touching first lateral processes. Basal segment short, not longer than wide, second and third segments armed with few setae. Fourth segment subequal to fifth, both armed with ectal and endal rows of several setae. Sixth segment armed with several short setae and several longer distal setae. Strigilis segments increasingly shorter and smaller, armed with dorsodistal seta each, and two rows of denticulate spines, the larger row with the formula 5 : 3 : 2 : 3, and the smaller row of spines in the formula 5 : 3 : 2 : 1. The larger spines with 5 or 6 serrations per side, the smaller spines with 1 or 2 serrations per side. Terminal claw slightly longer than terminal segment, without serrations or teeth.

Legs moderately long and slender, brachytarsal. First coxa without tubercles, armed with 2 dorsodistal setae and few short lateral setae. Second coxa armed with 2 long dorsolateral setae, several short setae, and a short genital spur with short distal setae. Third coxa subequal to first, armed with few ventral and several distal setae. Femur equal in length to second tibia, first tibia slightly longer. Femur armed with several ventral setae and 6 distal setae, 3 of which are longer than segment diameter. Single cement gland a very large sack filling almost half of femur, culminating in a low broad cone containing the gland tube exiting through a tiny pore. Distal to gland is 1 short seta. First tibia armed with 4 dorsal setae originating from low tubercles, the setae longer than the segment diameter, with lateral and distal shorter setae and several short ventral setae. Second tibia with corresponding 4 dorsal setae on tubercles, 3 shorter dorsal setae, and several ventral short setae increasing in numbers distally. Tarsus and propodus alike on all legs. Tarsus rectangular, slightly longer than wide, armed with 1 dorsodistal seta, several lateral setae and 6 or 7 ventrodistal setae. Propodus short, slightly curved dorsally, sole straight, armed with 5 or 6 short sole spines, several short lateral setae and 8 or 9 dorsal setae, some longer than segment diameter. Claw robust, well curved, slightly over half propodal length.

MEASUREMENTS OF HOLOTYPE (mm).—Trunk length (chelifore insertion to tip 4th lateral processes), 1.99; trunk width (across 2nd lateral processes), 1.13; proboscis length, 1.2; abdomen length, 0.56; third leg, coxa 1, 0.6; coxa 2, 1.09; coxa 3, 0.6; femur, 2.28; tibia 1, 2.62; tibia 2, 2.28; tarsus, 0.38; propodus, 1.02; claw, 0.52.

ETYMOLOGY.—The specific name is from the Latin prosus (turned forward or onward) and pertains to the large forward-leaning ocular tubercle.

DISTRIBUTION.—Known only from the type-locality in Sagami Bay, off Shimoda, in 30 meters.

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