SHRIMPS FROM THE MARSHALL ISLANDS CHACE 19 



of being 6-jointed. Antennal scale (fig. 8,/) reaching about to end of 

 antennular peduncle, the outer spine reaching barely as far as distal 

 margin of blade. Antennal peduncle reaching to about middle of 

 distal antennular segment. Third maxillipeds (fig. 8,0 barely over- 

 reaching antennal scale. First and second legs with a rudimentary 

 exopod as in some, if not all, other species of Athanas. First legs in 

 adult male (fig. 8,m-o) little unequal, extending beyond antennal scale 

 by about one-fifth of the merus; coxa armed with a strong, sharp 

 spine anteriorly. First legs in female (fig. S,p) with merus and chela 

 subequal in length and about 1.3 times as long as carpus. Second 

 legs (fig. 8,g) reaching nearly to end of antennal scale; carpus with 

 first joint slightly longer than other four together, second, third, and 

 fourth subequal and each less than one-half as long as fifth. Third 

 legs (fig. 8,r) extending beyond antennal scale by length of dactyl; 

 fourth legs (fig. 8,s) reaching just about to end of scale; and fifth legs 

 (fig. 8,0 extending to about middle of antennal scale. Dactyls of 

 last three legs simple, not biunguiculate. 



The mouthparts are as shown in figure 8,g-k. 



Most of the males in this collection lack one or both of the first 

 pair of legs, so that it is not certain whether these legs are sometimes 

 strikingly asymmetrical or not. In all males having carapace lengths 

 from 2.5 to 2.7 mm., however, the remaining leg, if present, is small, 

 approaching the condition in the female. At a carapace length of 2.9 

 mm. the remaining leg is of intermediate size. One larger male, with 

 a carapace length of 3.1 mm., has both legs large but somewhat more 

 asymmetrical than in the type. 



The male holotype is approximately 10 mm. long and has a carapace 

 length of 3.1 mm. The other males from the type locality have cara- 

 pace lengths of from 2.5 to 3.7 mm., the ovigerous females from 2.5 to 

 3.2 mm. The male from Namu Island, Bikini Atoll, has a carapace 

 length of 3.4 mm., and the ovigerous females from Tufa Island, Ronge- 

 lap Atoll, have carapace lengths of 3.4 and 3.5 mm. 



This species is named with some hesitation because of the numerous 

 similar forms now known from the Indo-Pacific region. All of the 

 specimens differ uniformly in certain particulars from previous de- 

 scriptions, however. The present form differs as follows from those 

 species in which the supracorneal spines are lacking and the dactyls 

 of the last three pairs of legs are simple: From A. crosslandi Tattersall, 

 1921, it is distinguished by the shorter rostrum and extracorneal teeth 

 and the longer stylocerite. From A. dimorphus Ortmann, 1894, by 

 the shorter stylocerite and shorter and more robust appendages. 

 From A. esakii Kubo, 1940, by the longer stylocerite and much smaller 



