396 BULLETIN 129^ UNITED STATES NATIONAL MUSEUM 



Description. — Carapace wider than long in large specimens and 

 usually longer than wide in small ones. The surface may be closely 

 paved with tubercles, very unequal in size and elevation and granu- 

 late, not smooth as in M. pilosus; sometimes, as in the small type- 

 specimen, the tubercles are almost absent from the furrows and lower 

 parts of the carapace. The largest and most prominent tubercles 

 are arranged as follows: One on each epigastric lobe; a transverse row 

 of four on protogastric lobes; three median mesogastric; one urogas- 

 tric; a line of three on the cardiac region 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 the extremities of 

 this curve are continuous with a line of granules and tubercles which 

 border the posterior margin. Numerous smaller tubercles and 

 granules are scattered and clustered about the larger tubercles; a 

 row of granules just within and parallel to posterior margin of 

 mesogastric region. 



The rostral horns in the immature taper to a point and curve 

 inward, inclosing a suboval sinus open anteriorly; with age, the 

 sharp tips disappear, the rostrum becomes relatively shorter and 

 more truncate. The same change takes place in the preorbital spine 

 and in the most anterior spine of the basal article of the antenna. 

 Four strong, antero-lateral spines, roughened with granules, the last 

 three sinuses bearing a secondary spine; a small, postero-lateral spine 

 just above margin. Outer orbital tooth flattened, tip rounded; two 

 supra-orbital lobules, one well-defined, the other insignificant, on 

 the posterior slope of the preorbital spine; on the lower margin of the 

 orbit are two subequal spines, one of which is on the basal antennal 

 article; there are three other spines on the same article, one just 

 below the first movable segment of the antenna, one (mentioned 

 above) just outside the same segment but not marginal; the four 

 spines form two parallel, oblique rows, the inner row continued on 

 the subhepatic region by four spines or tubercles. 



Chelipeds of moderate size, longer in tlie adult than the first leg, 

 although the merus is not much stouter than that of the leg. Merus 

 armed with 7 or 8 spines on outer or posterior margin, and a row of 

 smaller and more numerous spines within the margin above and 

 below; 3 spines on inner margin; a row of tubercles on lower margin; 

 a shorter, secondary row of tubercles on upper surface; the most 

 distal spines are the longest. Carpus covered with unequal, spaced 

 tubercles, 3 of which, of small size, are on the inner margin. Manus 

 unarmed. 



Legs longer and slenderer than in M. pilosus; merus armed above 

 with two rows of spines which increase in size toward the distal end 



