68 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
at antero-external angle, the third equally large at antero-internal angle. Orbital border with only 
three tubercles. Lateral margins armed with five almost cylindrical spines, which are simple and 
directed almost forward: the first and fifth are smallest; the fifth is post-lateral. Three strong projec- 
tions on branchial regions. Wrist with a large tubercle on inner margin; otherwise the feet resemble 
those of M. hispidus. Sternal plastron deeply hollowed anteriorly for seventh abdominal segment; 
sixth abdominal segment very wide in its anterior part. Merus of outer maxillipeds longer and much 
less deeply cut at its inner angle than in M. hispidus. 
Carapace a violet brown; claws and feet spotted with a wine-colored violet (A. Milne Edwards) . 
Dimensions of male: Length, 65 mm.; extreme width, 78 mm. (A. Milne Edwards). 
Guadeloupe (type locality). This species was not found by the Fish Hawk party, nor is it 
recorded by Gundlach, but I chanced to note in the Museum at Berlin, in 1896, a small male, labeled 
“Porto Rico. Gundlach.” The spots on the chelipeds were a striking feature of the preserved 
specimen. 
Mithrax depressus A. Milne Edwards. 
Mithrax depressus A. Milne Edwards, Crust. R6g. Mex., 96, pi. xx, f. 4, 1875 
Closely allied to M. hispidus. Carapace narrower across branchial regions; antero-lateral margins 
more arcuate than in M. hispidus, that is, after curving well outward anteriorly, they turn inward near 
lateral angle more than in that species. Tubercles of carapace prominent; on gastric region there are 
five tubercles in a transverse row, and in front of these two pairs of tubercles, the anterior pair at base 
of the rostral horns; on mesogastric region are two tubercles on each side in a transverse line; on 
branchial region the four principal tubercles form a rhomboid; in front of anterior of these tubercles 
are two or three smaller ones; near posterior margin of branchial region are about eight unequal 
tubercles forming two irregular rows. Space between the rostral horns U-shaped and narrower than 
either horn. Anterior of lateral branchial spines more swollen than in if. hispidus and blunter; spine 
on its front margin is reduced, tubercles above are enlarged; tubercles present on second and third 
branchial spines also. Arm with two blunt spines on anterior margin, the distal one large, proximal 
one small. Otherwise as in M. hispidus. 
Dimensions of male: Length, 43.5 mm.; width, 51 mm. 
Bahamas; Florida Keys, to 19 fathoms; AVest. Indies; off Cape St. Roque, Brazil, 20 fathoms; off 
the Abrolhos, Brazil, 30 fathoms ( Hassler ); Bermudas. Porto Rico: Hucares, 2 males; young sjjeci- 
mens were taken at the following stations: Off Puerto Real, 8$ fathoms, station 6074; off St. Thomas, 
20 to 23 fathoms, stations 6079, 6080; off Vieques, 6 to 14 fathoms, stations 6085, 6096; off Culebra, 15 
to 16 fathoms, stations 6090, 6093; off Humaeao, 91 to 121 fathoms, stations 6098, 6099. 
Mithrax pleuracanthus Stimpson. 
Mithrax pleuracanthus Stimpson, Bril. M. C. Z.,ii, 116, 1871: A. Milne Edwards, Crust. Reg. Mex., 95, pi. xx, f. 3, 1875. 
Mithraft hispidus Rathbun, Proe. U. S. Nat. Mus., xv, 265, 1892 (part). 
In 1892 (loc. cit. ) I believed M. pleuracanthus to be synonymous with M. hispidus; since then I 
have reconsidered the question and have examined more material, including type specimens of M. 
depressus, and have come to the conclusion that these three species can be maintained. The differences 
are very subtle, and not evident without careful study. The form of the carapace in M. pleuracanthus 
resembles that of M. hispidus; the third or posterior branchial spine is longer, and the second spine 
shorter, than the first; there are several tubercles about the base of each lateral spine. The tubercles 
of the carapace are well marked as in M. depressus. The two tubercles of each pair on the mesogastric 
region are confluent. The rostral horns of M. pleuracanthus are shorter and wider than in M. hispidus 
or M. depressus, and the interspace is narrower and inclines toward the triangular. The arm has on its 
anterior margin either a single spine, or a spine with a tubercle on its proximal slope. I may add 
that in young specimens these differences are less evident, making it almost impossible to separate 
the species with certainty. 
Dimensions of male: Length, 33.6 mm.; width, 40.7 mm. 
Florida Keys; AA^est Indies; Gulf of Mexico. Depth, 3 to 125 fathoms. Porto Rico: Off ATeques, 
14 fathoms, station 6085, 1 male, 3 young; off Humagao, 12J fathoms, station 6098, 1 young; San 
Juan (G. M. Gray). 
