MUSEUM OF COMPARATIVE ZOOLOGY. 19 



Catapagurus gracilis. 

 Eemipagurus gracilis Smith, Proc. National Mus., Washington, III. p. 426, 1881. 



This is a smaller and more slender species than the last, and is readily dis- 

 tinguished from it by the smooth carapax, the longer and more slender eye- 

 stalks, the long and acicular ophthalmic scales, and by the narrow dactyli of 

 the ambulatory legs being longer than the corresponding propodi. 



Male. — The carapax in front of the cervical suture is flat, smooth, nearly 

 naked, and scarcely at all JR^olated. The anterior margin is rather more 

 strongly sinuous than in C. socialis, and the lateral lobes are slightly angular 

 and each is tipped with a minute spine, as in that species, but the marginal 

 carina between these spines is much less distinct. 



The eye-stalks are more than half as long as the carapax in front of, the 

 cervical suture, flattened and expanded distally, but only about half as broad 

 as long. The eyes themselves are as in C. socialis. The ophthalmic scales are 

 more than half as long as the eye-stalks, and are acicular and regularly acute. 



The ultimate segment of the peduncle of the antennula is as long as the eye- 

 stalk and nearly twice as long as the penultimate segment. The major flagel- 

 lum is as long as the ultimate segment of the peduncle, the basal portion of 

 about eight segments, the terminal portion three times as long and of about 

 five subequal and very slender segments. The minor flagellum is about half 

 as long as the major, and composed of about six segments. The antennae are 

 very much as in C. socialis. 



The chelipeds are nearly equal in length and similar to those of C. socialis, 

 but in the right cheliped the inner edge of the upper surface of the carpus is 

 angular, and armed with a regular series of twelve to eighteen small spines, 

 while the outer edge is rounded and imarmed ; and the prehensile edge of the 

 dactylus is armed with two irregular and indistinct teeth, corresponding with 

 two irregular emarginations in the edge of the digital portion of the propodus. 

 In the left cheliped the outer edge of the upper surface of the carpus is slightly 

 rounded and scarcely at all spinulous, while the inner edge is armed as in the 

 right cheliped. The left chela differs from that of C socialis, in having the 

 digital portion of the propodus considerably stouter than the dactylus, particu- 

 larly toward the base. 



The ambulatory legs are proportionally as long as in C. socialis, but more 

 slender ; in both pairs the dactylus is longer than the propodus, curved slightly 

 near the tip, about sixteen times as long as broad, sparsely ciliated along the 

 upper edge, and very slightly setigerous along the lower. 



The female diflfers from the male as in C. socialis, but to a very much less 

 extent, the chelipeds and ambulatory legs being only a Little shorter than in 

 the male, and the right cheliped only a little less stout and a little more like 

 the left than in the male. 



The eggs are few and nearly as large as in C. socialis. 



The carcincecia are similar to those of the last species. 



