1879.] ree [Kingsley. 
Carapax naked, depressed, deeply areolate, areolations less broken 
than in WM. sculptus, punctate, a transverse of five tubercles on the 
gastric region and two more acute ones on the outer posterior por- 
tion of each branchial region, two prominent tubercles at the base 
of the rostrum, one on each side of the median line. Rostrum short, 
bifid, outer margins of horns arcuate, inner straight. Orbits with 
one distinct fissure above, inner angle prominent, rounded; outer 
also rounded but less prominent; external hiatus a rounded opening. 
Antero-lateral margin with three teeth, besides the external angle of 
the orbit, first and second teeth stout, prominent, obtuse, the second 
the larger; third tooth slender, acute, hooked forward; a small acute 
tooth on the postero-lateral margin behind. the lateral angle. A 
tubercle on the subhepatic region beneath the first tooth of the 
antero-lateral margin. An oblique row of rounded tubercles run- 
ning backward from the palatal region. Basal joint of antenna 
with two short blunt teeth. Chelipeds small; posterior margin of 
meros four toothed, upper surface with one tooth, inner margin with 
a single rounded tubercle; carpus prominently tuberculate; hand 
smooth, inflated, cristate above at the base, a small depressed 
tubercle on the outer surface at the articulation with the carpus; 
fingers moderately gaping, denticulated at the extremity, a basal tooth 
on the dactylus in both sexes, but the larger in the male. Am- 
bulatory feet with spinous tubercles on the basal joints, becoming 
obsolete on the distal ones; dactyli strongly arcuate. Specimens 
from the Gulf of California sent by Mr. Lockington have the follow- 
ing dimensions. 
Length of carapax, 7, 11 mm., ?, 11.7 mm.; breadth, ¢, 13.5 mm., 
fepasmim.: ratio, J, 1: 1.23, 9, 1: 1.28. 
This species differs from M. cinctimanus, denticulatus, hirsutipes (sp.n.) 
and minutus (Mithrax minutus Saussure) in having but three teeth on 
the antero-lateral margin; from M. denticulatus, ruber, hirsutipes and 
sculptus in the presence of a basal tooth on the dactylus of the 
chelipeds; from M. sculptus, cinctimanus and coronatus in having the 
ridge running backward from the palatal region tuberculate; from 
M. nodosus in having the orbit fissured above, and in the more acute 
lateral tooth. It appears to be most closely allied to M. ruber but lacks 
the sinuous character of the anterior margin of the external max- 
illipeds, found in that species. 
Mithraculus hirsutipes sp. n. 
Carapax smooth, naked, sculptured, with four tubercles on the 
