THE SPIDER CRABS OF AMERICA 409 



Off Abrolhos Islands, Brazil; 30 fathoms; 1872; U. S. C. S. S. 

 Hassler; 1 young female (1993, M. C. Z.) ; " Mithraculufs coronatiLs" 

 (A. Milne Edwards) . 



Abrolhos Islands, Brazil; December 27, 1887; Albatross; 1 male 

 (21949), variety. 



Rio de Janeiro, Brazil; received December 1, 1863; G. N. Davis; 



1 male, 1 female (1954, M. C. Z.), variety. 

 Brazil; 1 very large male (Copenhagen Mus.). 

 Bermuda; 1876-1877; G. Brown Goode; 1 male (41523). 

 Bermuda; T. H. Bean; 1 male, 1 female (21605). 



Locality not given: One female, type (Berlin Mus.). One male, 

 imusually rough (13937). From Bureau of Fisheries; 1 female 

 (32237). 



MFFHRAX (MITHRAX) CARIBBAEUS Rathbun 



KNOBBED CRAB 

 Plates 148 and 149 



Mithrax hispidus Benedict, Johns Hopkins Univ. Circ, vol. 11, No. 97, 

 Apr., 1892, p. 77. — Rathbun (part), Proc. U. S. Nat. Mus., vol. 15, 

 1892, p. 265; Bull. U. S. Fish Comm., vol. 20 for 1900, pt. 2 (1901), p. 

 67 (specimen from Guanica). 



Mithrax depressus Rathbun (part). Bull. U. S. Fish Comm., vol. 20 for 

 1900, part 2 (1901), p. 68 (specimens from Hucares). 



Mithrax caribbaeus Rathbun, Proc. Biol. Soc. Washington, vol. 33, 1920, 

 p. 23 (type-locality, St. Thomas; holotype. Cat. No. 50363, U.S.N.M.); 

 Univ. Iowa Studies Nat. Hist., vol. 9, 1921, p. 83, pi. 3. 



Diagnosis. — Two parallel, transverse, or nearly transverse rows of 

 three tubercles or tubercles and spines on postero-lateral region of 

 carapace; at least three of these are of good size. Rostral sinus 

 U-shaped, about as wide as each horn. Two stout spines on ante- 

 rior margin of arm; the proximal one may be bifid. Crenulation 

 or tuberculation of prehensile edges of fingers persisting in the old. 



Description. — This species is very closely related to M. hispidus, 

 which it approaches in its large size. Rostral horns longer than in 

 hispidus, and a little less truncate. Carapace a little narrower, ap- 

 proaching the shape of pleuracanthus. This species differs from all 

 its allies in the arrangement of tubercles or tubercles and spines on 

 the postero-lateral region. There is a postero-lateral spine in smaller 

 specimens which becomes a tubercle in older ones. This forms the 

 outermost unit of a transverse row of 3, which is subparallel to another 

 anterior row of 3 tubercles. Anterior margin of arm provided with 



2 conical spines; the only exceptions are the holotype which is un- 

 usually large and has the proximal spine bifid and the smallest speci- 

 men (16192) in which the proximal spine of the right side is missing. 



The chelae of the large specimen differ from those of hispidus of 

 similar size in having the palm shorter and the fingers longer than in 



