THE GEAPSOID CEABS OF AMERICA. 



173 



OPISTHOPUS TRANSVERSUS Rathbun. 



Plate 37, figs. 4 and 5. 



Opisthopus transvcrsus RATHBUN, Proc. U. S. Nat. Mus., vol. 16, 1893, p. 

 252 (type-locality, Monterey, California ; female holotype, Cat. No. 

 3446, U. S. N. M.) ; Harriman Alaska Exped., vol. 10, 1904, p. 188, pi. 9, 

 fig. 2, text-fig. 95. HOLMES, Occas. Papers California Acad. Sci., vol. 7, 

 1900, p. 97. WEYMOUTH, Leland Stanford Jr. Univ. Publ., Univ. ser. 

 No. 4, 1910, p. 61, text-fig. 9. 



Diagnosis. Carapace little transverse, suboblong, convex, even, 

 firm. Legs similar, second longest, but not notably so; dactyli 

 curved. 



Description of female. Carapace highest in middle, whence it 

 slopes downward in all directions. Some shallow depressions par- 

 tially inclose the various regions. A border of pubescence along 

 part of antero-lateral margin. True lateral margin of carapace not 



PIG. 110. OPISTHOPUS TRANSVERSUS, FEMALE (23927). a, DORSAL VIEW, X 1$ ; b> EN- 



DOGNATH OP OUTER MAXILLIPED, X 8. 



visible in dorsal view. Front not visible from above; in anterior 

 view it is triangular, being longer in middle than at outer angles. 

 Orbits a broad oval, filled by eyes. 



Chelipeds of good size, pubescent, and with margins of merus 

 and inner surface of carpus and propodus hairy; palm increasing 

 slightly in width to distal end, lower margin convex; fingers elon- 

 gate, nearly horizontal, not gaping, one small tooth at base of 

 dactylus and two or three at base of pollex. tips hooked and crossing 

 each other. 



Legs thick, pubescent, margins hairy, second leg longest, third 

 similar, reaching middle of dactylus of second, first pair a little 

 shorter than third, fourth pair shortest, reaching middle of pro- 

 podus. Margins of merus joints subparallel. Dactyli strongly 

 curved. 



/Sexual variation. Male much smaller and less convex than female, 

 front less deflexed and pubescent. Chelae shorter and higher, thumb 

 shorter. Abdomen tapers regularly from third to last segment. In 



