THE SPIDER CRABS OF AMERICA 141 



F'. No postorbital tooth or spine. Rostrum, in American species, 

 bifurcate for half its length, horns widely divergent. 



Menaethiops, p. 189. 

 F-. A postorbital tooth. Carapace with two lateral expansions, one 

 or both more or less laminate, the hepatic expansion subdivided, 

 its anterior portion forming a postorbital tooth or lobe. 

 G'. Lateral expansions both very broad, inwardly united, out- 

 wardly marked by a closed fissure Mimulus, p. 182. 



G^. Lateral expansions narrower and separated bj^ a sinus. 



Pugetti a, p. 167. 

 E^. Antennae not visible in dorsal view at sides of rostrum. 



F'. Rostrum short, triangular, partly divided by a closed median 



slit. Legs more or less cristate leucippa, p. 184. 



F^. Rostrum long, two-horned. Legs not cristate. 



Sphenocarcinus, p. 185. 



Genus ACANTHONYX Latreille 



Acanihonyx Latreille, Encyc. M6th., Hist. Nat., Insectes, vol. 10, 1825, 

 p. 698; tj^pe, A. lunulatus (Risso); Cuvier's Regne Anim., ed. 2, vol. 4, 

 1829, p. 58.— Milne Edwards, Hist. Nat. Crust., vol. 1, 1834, p. 342 

 (part). — A. Milne Edwards, Crust. Reg. Mex., 1878, p. 142. — Miers, 

 Journ. Linn. Soc. London, vol. 14, 1879, p. 650; Challenger Rept., Zool., 

 vol. 17, 1886, p. 42. — Alcock, Journ. Asiat. Soc. Bengal, vol. 64, 1895, p. 

 198.— Rathbun, Bull. U. S. Fish Comm., vol. 20, for 1900, pt. 2 (1901), 

 p. 60. 



Meria Griffith, Cuvier's Animal Kingdom, vol. 13, 1833, p. 165, in sy- 

 nonymy of Acanthomjx; type, M. glabra Griffith. Not Meria Rossi, 1807 

 (Hymenoptera). 



Peltinia Dana (part), Amer. Journ. Sci., ser. 2, vol. 11, 1851, pp. 272 and 

 433; U. S. Expl. Exped., vol. 13, Crust., pt. 1, 1852, pp. 84 and 129; vol. 

 2, 1853, p. f422. 



Carapace suboblong, rounded behind, almost smooth, not markedly- 

 constricted behind the prominent antero-lateral angles, the lateral 

 branchial spines small and not prominent. Preocular spine or lobe 

 prominent. Orbits small, entirely filled by the stout eyestalks; 

 corneal end small. No postorbital tooth. Spines of rostrum united 

 at base, acute, little divergent. Antennae visible at sides of rostrum. 

 Merus of outer maxillipeds transverse, dilated at antero-external 

 angle, slightly notched at antero-internal angle. 



Chelipeds of adult male well developed; palm compressed, but 

 slightly turgid in the middle, often slightly carinate above; fingers 

 acute, gaping when closed. Legs short, rather stout,*decreasing in 

 length successively from first to fourth pair, compressed; penulti- 

 mate article more or less dilated, the posterior margin concave and 

 setose near end, at broadest part forming a blunt tooth against 

 which the dactylus fits like a claw, when flexed; dactylus spinous on 

 posterior margin. Abdomen of male with five or six segments. 

 5487- 25t n 



