THE BRACHYURA AND MACRURA OF PORTO RIOO. 
67 
Mithrax plumosus, sp. nov. 
Mithrax aculeatus Rathbun, Proc. U. S. Nat. Mus., xv, 264, 1892. (Not M. aculeatus (Herbst) Milne Edwards.) 
Mithrax verrucosus variety, Rathbun, Ann. Inst. Jamaica, I, 9, 1897. 
Carapace wide, little swollen, and covered with very flat and crowded granules, with some raised 
tubercles toward lateral and frontal margins; surface covered (but not sufficiently to obscure the granu- 
lation) with plumose bristles and tufts of longer, stiffer bristles arising from each tubercle. Rostral 
horns short, truncate, interspace wider than horn. Preorbital tooth blunt, directed a little outward. 
Basal article of antenna with three blunt spines; the orbital border has, besides, four blunt spines. 
Antero-lateral margin armed with four slender subacute spines, of which the first three are double; the 
anterior of each double spine is the smaller; a short postero-lateral spine. Inner margin of arm and 
wrist armed with sharp spines; upper surface spinous; arm with five or six sharp spines on outer 
margin; hand with a few spinules on ujiper surface near wrist. Palm and fingers otherwise smooth, 
naked, and shining. The rest of the chelipeds and also the ambulatory legs hairy like carapace. Meral 
and carpal joints of ambulatory legs spinous. Young specimens have the rostral horns relatively longer 
and sharper; the hand is rougher than in the adult and hairy at the proximal end. 
This species I at first mistook for M. aculeatus (Herbst), and later thought it might be a variety 
of M. verrucosus, to which it is most closely related. M. aculeatus (Herbst), now M. pilosus, is furnished 
with much stronger lateral spines and the setae covering the surface are denser and all of the same 
character. M. verrucosus, on the other hand, has the carapace bare or nearly so, and the hand and 
upper surface of the wrist are unarmed; the young have the rostral horns relatively' shorter than the 
adult, while the reverse is true in M. plumosus. This species is of more frequent occurrence than either 
of those with which it has been confounded. 
An ovigerous female from Puerto Real measures BO mm. long, including horns, and 35.8 nun. wide, 
including spines. This specimen may be taken as the type (Cat. No. 23775). Also found in Porto Rico 
at Boqueron; reefs at Ponce; Arroyo; Caballo Blanco Reef, Vieques; Ensenada Honda, Culebra; 
Fajardo. Bahamas; Florida Keys; West Indies; Fernando Noronha. 
Mithrax hispidus (Herbst). 
Cancer hispidus Herbst, Natur. Krabben u. Krebse, I, 247, pi. xvm, f. 100, 1790. 
Mithrax hispidus Milne Edwards, Mag. Zool., ii, 1882; A. Milne Edwards, Crust. ROg. Mex., 93, pi. xxi, f. 1, 1875. 
Carapace swollen, considerably wider than long, smooth, except for some low, rounded promi- 
nences chiefly toward the outer margin of the branchial region. Gastric tubercles very faint. Front 
wide; horns short, obtuse, interspace U-shaped, as wide as either horn. Preorbital angles blunt, 
slightly produced. Basal joint of antenna with two teeth, inner one nearly reaching line of rostrum, 
the other smaller, on orbital border; besides, the orbit has four tubercles on margin, two superior, 
much smaller than external or inferior tubercle. Lateral margin armed with five spiniform teeth; the 
first obtuse, often bifid at extremity; the second longer, sharp and double, curving forward; third 
and fourth more slender and about the same length; fifth postero-lateral, much smaller, and situated 
higher up on carapace. Subhepatic region with two tubercles; a number of tubercles, some of them 
pointed, are on the subbranchial and pterygostomian regions. Arm with four or five spines on upper 
margin; two on inner margin; and a few tubercles on the upper surface. Wrist smooth; inner margin 
evenly rounded. Hand smooth; fingers narrowly gaping; a broad, low tooth near the base of the 
dactylus. In young specimens the tubercles of the carapace are more protuberant. 
Dimensions of male: Length, 86.5 mm.; width, including spines, 114 mm. 
Bahamas; Florida Keys; West Indies; Venezuela; Bahia and Abrolhos Islands, Brazil; Bermu- 
das. Guanica, Porto Rico; San Juan (Gundlach). 
Mithrax lievimanus Desbonne & Schramm. 
Mithrax Isevvmanus Desbonne & Schramm, Crust. Guadeloupe, 7, pi. i, figs. 1 and 2, 1867; A. Milne Edwards, Crust. R6g. 
Mex., 94, pi. XXI, f. 2, 1875. 
Resembles M. hispidus; the carapace smooth, and having only a few rounded prominences, but 
narrower; the front also is narrower and much more produced. Preorbital projections rounded. 
The basal article of antenna bears three blunt spines, one below insertion of next article, one stronger 
