30 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL.21 



2a. Chelipeds specially mobile, rarely much greater than the 

 other legs, or with fingers bent at an angle on the hand. 

 Second article of antenna well developed, generally fused 

 with epistome and often with front. Orbits generally more 

 or less incomplete. Hooked hairs almost always present 

 Majidae 



2b. Chelipeds not specially mobile, usually much longer and 

 heavier than the other legs, and with fingers bent on the 

 hand at an angle toward the side on which the fixed finger 

 is set. Second article of antennae small, short, and not fused 

 with epistome or front. Orbits well made. Hooked hairs 

 almost always wanting Parthenopidae 



Family HYMENOSOMIDAE 



Hymenosomidae Stimpson, 1858, p. 108. Ortmann, 1893, p. 31. Alcock, 

 1900, pp. 285, 291, and 385. Borradaile, 1907, p. 480. Rathbun, 

 1925, p. 561. 

 Hymenosomatidae Stebbing, 1905, p. 49. Stephensen, 1945, p. 217. 



Carapace thin, flat, triangular or subcircular, not very well calcified, 

 usually produced to form a horizontal rostrum. Antennular fossae shallow 

 and ill defined. Antennal peduncle slender. Buccal cavern square; 

 epistome sometimes nearly as long as broad. The ischium of the external 

 maxillipeds well developed ; the palp articulating near the anteroexternal 

 angle of the merus ; the exognath slender and partly or entirely concealed. 

 Male openings sternal. (Alcock) 



Carapace thin and flat. Chelipeds not long or specially mobile or 

 with fingers bent at an angle with the hand. Male openings sternal. No 

 orbits; [eyes exposed and little retractile]. Second [segment] of antennal 

 stalk slender, fused with epistome but not with front. No hooked hairs. 

 (Borradaile) 



Pleopod 1 varying, especially in the apex. Pleopod 2 short. (Stephen- 

 sen) 



Genus HALICARCINUS White 



Halicarcinus White, 1846, p. 178. Alcock, 1900, p. 291. Rathbun, 1925, 



p. 561. 

 Liriopea Nicolet, 1849, p. 158; type: Hymenosoma leachi Guerin, 1838 



= Halicarcinus planatus (Fabricius), by subsequent designation of 



Rathbun (1925). 



