478 BULLETIN 129, UNITED STATES NATIONAL MUSEUM 



spine. Suborbital, subhepatic and antennal regions armed with six 

 spines of which the four anterior are small, the two posterior large; 

 of the small spines one is situated at the insertion of the movable 

 part of the antenna, and three (two antennal and one orbital), 

 form a longitudinal row; one of the large spines is near the outer 

 angle of the buccal cavity, the other further back and out. 



Chelipeds of adult male rather slender, about as long as carapace. 

 Arm with two conical spines above, one terminal, one near proximal 

 end, also a line of three or four tubercles beneath, and two tubercles 

 on the outer surface. Proximal half of fingers gaping, a large tooth 

 at base of dactyl. Merus of ambulatory legs with a conical tooth 

 above at articulation with carpus. 



Measurements. — Male (15128), length of carapace measured to 

 posterior margin 21.5, length of horn 4, width of carapace between 

 tips of lateral spines 26.6, width just in front of these spines 17.3 

 mm. Female (15131), length of carapace 24, greatest width 27.7 

 mm. Female (Miers), length 41, width 32.5 mm. 



Range. — South Carolina to Gulf of Mexico; Bahia, Brazil (Miers). 

 Shallow water to 79, exceptionally 116, fathoms. 



Material examined. — See table, page 479. 



MACKOCOELOMA DIPLACANTHUM (Stimpson) 



Plate 169, fig. 1; plate 269, figs, 1-3 



Pericera diplacantha Stimpson, Ann. Lye. Nat. Hist. New York, vol. 7, 1860, 

 p. 183 (type-locality, St. Thomas; type not extant). — Schramm, in Des- 

 bonne and Schramm, Crust. Guadeloupe, 1867, p. 16, pi. 5, figs. 16-18. — 

 A. Milne Edwards, Crust. R6g. Mex., 1873, p. 55, pi. 13, fig. 2. 



Macrocoeloma diplacantha Miers, Challenger Rept., Zool., vol. 17, 1886, p. 79. 



Macrocoeloma diplacanthum Rathbun, Bull. U. S. Fish Comm., vol. 20 for 1900, 

 pt.2 (1901), p. 74. 



Diagnosis. — Postero-lateral process bifid. Rostral horns sub- 

 parallel. Five conical, dorsal tubercles. 



Description. — Surface ornamented with rows of long, curved hairs, 

 one row leading from each branchial region forward along the upper 

 surface of the rostrum, another row along the sides of the carapace. 

 Carapace narrow, subtrigonal, much elevated. Four conical tuber- 

 cles form almost a rectangle near the center of the carapace, while a 

 fifth, more spiniform elevation occupies the intestinal region. Postero- 

 lateral process rather long, flattened and double, seerning to consist of 

 two spines, one above the other, connected nearly to their tips by a 

 web-like connecting lamina, concave anteriorly, convex posteriorly. 

 Antero-lateral margin concave, unarmed except with a small hepatic 

 tubercle. Gastric region strongly inclined anteriorly, with the 

 frontal region (Stimpson) . The rostrum is long, varying from nearly 

 one-third to two-fifths of the entire length of the carapace; horns 



