THE SPIDER CRABS OF AMERICA 193 



Subfamily PisiNAE 



Pisinae Alcock, Journ. Asiat. Soc. Bengal, vol. 64, 1895, p. 165. 



Blastidae Stebbixg, Marine Invest. S. Africa, vol. 4, Cape Town, 1905, p. 25. 



Eyes witli commencing orbits, of which one of the most character- 

 istic parts is a hirge, blunt, usually but not always isolated, cupped 

 postocular process into which the eye is retractile, but never to such 

 an extent as to completely conceal the cornea from dorsal — still less 

 from ventral — view; there is almost always a distinct supraocular 

 eave, which is often produced forwards as a spine; the eyestalks are 

 short. The basal antennal article is usually rather broad, at any 

 rate at the base; its antero-external angle is generally produced 

 forwards as a spine or tooth. The merus of the external maxillipeds, 

 owing to the expansion of its antero-external angle, is broader than the 

 ischium and carries the palp at its antero-internal angle. Rostrum 

 usually two-spined or two-toothed. Legs often very long. (After 

 Alcock.) 



KEY TO THE AMERICAN GENERA OF THE SUBFAMILY PISINAE 



A'. Supraocular save not in close contact with the postocular spine or process. 

 B'. No tooth on orbital margin between supraocular eave and postocular cup. 

 O. Supraocular eave produced anteriorly in a spine. (In the genus Rochinia, 

 this is true of American species.) 

 D'. Rostrum bifid for more than half its length. 



E'. Rostrum thin, broad, flat and horizontal. Movable articles of 

 antennal peduncle laterally carinate; palms carinate above. 



Carapace lumpy , Scyra, p. 195. 



E^. Rostrum armed with two long slender spines, or thick and deflexed. 



F'. Rostrum thick and deflexed. Supraocular eave widespreading, 



separated from the postocular tooth by a broad V-shaped sinus. 



Large, hairy crabs Loxorhynchus, p. 198. 



F^. Rostral spines slender. 



G'. Ambulatory legs bordered with two rows of spines. 



Oplopisa, p. 228. 

 Gr^. Ambulatory legs not bordered with two rows of spines. 



H*. An orbital spine between postocular spine and basal antennal 

 article; orbit very open above; supraocular eave narrow, 

 its spine small. Chelae of male swollen. 



Trachymaia, p. 229. 

 H2. No orbital spine between postocular spine and basal 

 antennal article; supraocular eave advanced in a sub- 

 stantial spine. 

 J'. Chelipeds of male much enlarged; palm broad, upper edge 

 thin. Superior orbital sinus V-shaped. .Choriha, p. 202. 

 J-. Chelipeds slender, often greatly elongated in male. Orbi- 

 tal sinuses U-shaped and more open than in Chorilia. 



Rochinia, p. 204. 

 D^. Rostrum bifid at tip only, or at least not behind the middle. Cara- 

 pace broadly subtriangular. Preocular spine well developed. 

 E". Not more than two long, antero-lateral marginal spines. Inferior 

 orbital sinus rounded Libidoclaea, p. 223. 



