CRUSTACEA NORTH PACIFIC EXPLORING EXPEDITION l6l 



consider it specifically, or even generically, different from Xursilia 

 dentata. It certainly shows a much greater difference between the 

 male and female than is noticed in other genera of the family. The 

 variation, however, when it exists, is usually found in the outer max- 

 illipeds, as the ciliated ridge in the female, etc. 



Our specimen was dredged in ten fathoms, sandy bottom, in the 

 straits separating Katonasima from Ousima. 



CRYPTOCXEMID.^ 



A small but well-marked group of Leucosidea may be separated 

 under this title, including the genus Tlos White (which we conclude 

 to be a Leucosidian, notwithstanding Bell's footnote^, and the three 

 new genera described below. They are analogous to Cryptopodia 

 among Parthenopidse and to CryptoUthodcs among the Lithodidse, 

 being characterized by a broad, flattened, or even concave, carapax, 

 the margins of which are expanded and lamelliform, projecting so 

 much as to conceal the ambulatory feet for the whole or a part of 

 their length. The chelipeds are, as in Cryptopodia. large, depressed 

 and always exposed. The apex of the outer maxillipeds is sharply 

 triangular, projecting much beyond the extremity of the exognath, 

 and dividing the epistome into halves. The exognath is generally 

 dilated, and its outer margin more or less arcuated. The basal joint 

 of the outer maxillipeds is rather small. The pterygostomian chan- 

 nels are broadly excavated, with the inner margin distinct and 

 projecting only at the anterior extremity, posteriorly sloping off 

 smoothly inwards. The orbits are small and deep, and the outer an- 

 tennae obsolete, or nearly so. In the male abdomen the segments 

 seem to be mostly soldered together, the first and last being, how- 

 ever, always distinct. 



The crabs of this family would appear to have their nearest allies 

 among ordinary Leucosidae in Orcopliorus, Xursia, and NursiUa. 



Genus CARCIXASPIS Stimpson 



Carapax suborbicular, depressed, nearly flat, broader than long, 

 broadly rounded but not expanded posteriorly. Sides expanded, 

 but not projecting sufficiently to conceal entirely even the meros- 

 joints of the ambulatory feet. Front rostrate; rostrum short, 

 broadly truncated. Eyes concealed beneath the carapax. Orbits 

 very deep, round, without fissures, closed within and not communi- 



' Lin. Trans., xxi, p. 278. 

 II 



