THE BRACHYURA AND MACRURA OF PORTO RICO. 
69 
Mithrax ruber (Stimpson). 
Mithraculus ruber Stimpson, Bull. Mus. Comp. Zool., ii, 118, 1871. 
Mithraculus nudtis A. Milne Edwards, Crust. R6g. Mex., 110, pi. xxm, f. 2, 1875. 
Mithrax ruber Miers, Challenger Rept., Zool., xvn, 87, 1886. 
Mithrax nuclus Miers, Inc. cit. 
Carapace much wider than long; surface naked, polished, and uneven. A few smooth, rounded 
prominences are on branchial region; some small depressed tubercles are arranged in transverse rows 
on gastric region, and larger ones occur on cardiac and branchial regions. The lateral protuberances 
are four, the first two blunt, the last two sharp, spiniform, the third largest and most produced, the 
fourth post-lateral; a tubercle on anterior slope of the second tooth, a spine in the interval between 
second and third. Frontal horns very short, thickened, upturned, blunt; interspace narrow. Behind 
the horns two small prominences. Margin of orbit thickened, especially the preorbital lobe; a small 
tooth on upper margin; otherwise entire. Basal antennal joint rather narrow, with two lobes, one 
large and thick at antero-external angle and further advanced than preorbita! lobe, the other small, on 
outer margin. Chelipeds strong; arm with a single lobe at proximal end of anterior margin, four 
spines on posterior margin, and two spines on upper surface; wrist almost smooth; hand smooth; 
fingers denticulate except at base; the movable finger in the full-grown male bears a strong tooth near 
its proximal third; fingers gaping. Ambulatory legs spinous and hairy. 
Entire length of ovigerous female from Arroyo, 13 mm.; entire width, 15.8 mm. 
Mayaguez, on coral reef, one male; Playade Ponce Reef, two young; Arroyo, on Lighthouse Reef, 
1 female, 1 young. Cuba (Stimpson); Guadeloupe (Geneva Museum). 
Mithrax hemphilli Rathbun. 
Mithrax hemphilli Rathbun, Proc. U. S. Nat. Mus., xv, 263, pi. xxxvii, f. 2, 1892. 
Carapace oblong-triangular, covered with strong tubercles and granules. The largest tubercles 
are arranged as follows: One on either side of the middle, in a line with posterior margin of orbit; a 
transverse row of four on protogastric lobes; three median mesogastric; one genital; a line of three on 
the cardiac forming a transverse curve concave forward; behind these, one on median line; from 
seven to eight on branchial region, those most posterior being spinous; four spinous tubercles on 
intestinal region forming a transverse curve concave to posterior margin; the two tubercles at extremi- 
ties of this curve are continuous with a line of granules which borders the posterior margin. The two 
central protuberances of the marginal line are small tubercles. Numerous smaller tubercles and 
granules scattered or clustered about the larger tubercles; a row of granules just within and parallel 
to posterior margin of mesogastric region. Rostrum rather long for the genus, horns acute, curving 
inward at tip; outer margin finely denticulate. Preocular tooth long, acute, elevated, the tips being 
in a horizontal line with posterior margin of rostral sinus. The two sinuses of upper orbital margin 
are triangular and inclose a subtriangular, truncate tooth. Four antero-lateral spines, stout, conical, 
and embossed with granules and tubercles; also a few intermediate and much smaller spines; a short 
post-lateral spine just above margin. Basal joint of antenna armed with four spines and teeth; a long, 
slender spine at anterior outer angle, overreaching preorbital spine; a shorter spine or tooth on outer 
margin, forming one of two on the margin of orbital floor; at the base of the first movable joint a 
spiniform tooth just visible in a dorsal view; obliquely behind this is another tooth, succeeded by four 
others which cross the subhepatic region. Chelipeds rather feeble; arm with an upper and outer row 
of spines and four or five rows of tubercles; wrist tuberculous; hand smooth, with parallel margins; 
fingers showing only a small hiatus at. base when closed. Ambulatory legs spinous; the spines on the 
meral joints strong. 
Dimensions of male: Entire length, 19.8 mm.; entire width, 19.9 mm. 
Indian Key, Florida; Rio Formoso, Pernambuco; Abrolhos Islands, Brazil. Ensenada Honda, 
Culebra, 2 males, 1 female. 
Mithrax holderi Stimpson. 
Mithrax holdcri Stimpson, Bull. Mus. Comp. Zool., n, 117, 1871; Rathbun, Bull. Lab. Nat. Hist. State Univ. Iowa, i\ , 259, pi. 
Ill, f. 2, 1898. 
Carapace oblong, covered with unequal, prominent tubercles, and with large, crowded punctse. 
Frontal horns depressed, nearly horizontal, narrow, short, acute. Basal antennal joint with three 
spines, antero-external long, nearly as advanced as the rostrum and directed obliquely upward and 
