392 BULLETIN 129, UNITED STATES NATIONAL MUSEUM 



MITHRAX (MITHRAX) HOLDERI Stimpson 



Plate 138, figs, land 2; pi. 257, fig. 2 



Mithraec subspinosus Kroyer, MS. labels in Copenhagen Mus. 



Mithrax holderi Stimpson, Bull. Mus. Comp. Zool., vol. 2, 1871, p. 117 



(type-locality, Tortugas, 7 fathoms; type not extant). — Rathbun, Bull. 



Lab. Nat. Hist. State Univ. Iowa, vol. 4, 1898, p. 259, pi. 3, fig. 2; Bull. U. S. 



Fish Comm., vol. 20, for 1900, part 2 (1901), p. 69. 



Diagnosis. — Elongate, ovate-oblong. Carapace without dense pu- 

 bescence, but uneven with many areolae and tubercles. A well- 

 marked postero-lateral spine. 



Description. — Carapace suboblong, length definitely greater than 

 width, lateral angles far back. Carapace covered in the main with 

 small areolae, each of which is surmounted by from one to several 

 pointed granules or tubercles; the largest of these tubercles are four 

 which form an arch above the posterior margin and one above the 

 postero-lateral branchial spine. The surface has much the appear- 

 ance of a Microphrys. There are only two large antero-lateral mar- 

 ginal spines — one on the swollen hepatic region, and the other at the 

 lateral angle; in front of the latter, a small spine; one of intermediate 

 size on the postero-lateral margin ; all are hooked forward at the tip. 

 Rostral horns short, triangular, tips turned inward. The basal seg- 

 ment of antenna bears three spines, the one at the antero-lateral angle 

 longer than the rostral horns and reaching nearly as far forward, a 

 shorter one on orbital margin and a small but sharp one at the base 

 of the next segment. Movable portion of antennae bordered laterally 

 by long hairs. The margin of the orbit has, besides the postorbital 

 and the long preorbital spine, two small ones above and one below. 



Chelipeds of moderate size. The merus has an irregular row of 

 spines on upper margin, a few small spines either side, and two 

 tubercles on the lower, outer margin. Carpus sparingly tuberculated; 

 manus smooth. Legs long-hairy, stout, flattened above, the upper 

 surface of merus and carpus bordered by spines, propodus unarmed. 



Measurements. — Female (25567) , length of carapace, horns included 

 27; length, horns excluded, 25.3; width of same, spines included, 

 26.5; width, spines excluded, 23.4 mm. 



Variation. — The young are wider anteriorly, and the spines sharper. 



Range. — Florida Keys; Greater Antilles; Virgin Islands. Low 

 water to 21 fathoms. 



Material examined. — 



Ragged Keys, Florida; 1901; J. E. Benedict; 1 mature female 

 (25567). 



Cabanas, Cuba; Jime 8-9, 1914; Henderson and Bartsch, col- 

 lectors; station 16, Tomas BarreraEiXiped.; 1 young female (48746). 



Off Havana, Cuba; May 26, 1893; State Univ. Iowa Exped.; 1 

 female (Mus. S. U. I.). 



