190 Mr. J. Wood-Mason on a new 



HylcEOcarcinus Humei^ n. sp. 



The carapace is at once distinguished from tliat of Pelo- 

 carcinus Lcdanclei, M.-Edw., by its more arched outline in 

 front, and by the two rounded tubercles on the mesogastric 

 lobe, which, as in Gecarcinus ruricola, is limited off antero- 

 laterally from the rest of the gastric region by very shallow 

 depressions passing off from the hinder end of the profoundly 

 deep median groove, and joining the branchio-gastric groove 

 on each side ; the straight line representing its greatest breadth 

 crosses it just in front of these tubercles ; in front of this 

 imaginary line its upper surface is very convex and much 

 swollen everywhere, but behind it flat ; it is just perceptibly 

 angulated on each side for a short distance beyond the external 

 margin of the orbits, these angulations coiTesponding to the 

 lines of spiniform tubercles seen in the same position in 

 Oecarcimis ruricola. The outer slopes of the branchial re- 

 gions both anteriorly and posteriorly, and the floors of the 

 branchial chambers — all the inflected portions of the carapace, 

 in fact, covered with squamiform tuberculated lines, which, 

 fine and delicate above, become shorter and coarser as they 

 approach the bases of the legs and the buccal frame. The 

 anterior is divided by a shallow transverse impression, slightly 

 internipted in the middle line, from the posterior cardiac lobe, 

 which, just as in the rest of the Gecarcinidse, is much expanded 

 posteriorly between the bases of the posterior pair of legs. 



The interantennulary septum is formed mainly by the sub- 

 frontal lobe, but partly by a short triangular process of the 

 epistoma. The flagella of the antenna are rudimentary. Both 

 divisions of the suborbital lobes have their margins roughened 

 with small tubercles. 



The sternal region is much broader than long, its greatest 

 breadth being between the bases of the second pair of legs. 



The male appendages are very stout and long, reaching 

 beyond the fifth postabdominal somite, and are connected at 

 their bases with a remarkably stout and highly indurated 

 semicircular plate, which arches over the intestinal canal ; a 

 similar plate has been observed in the genus Cardisoma by 

 S. I. Smith *, and is doubtless present in all Gecarcinidge. 



Postabdomen of the female broadly oval, about as broad as 

 long, covering all but the margins of the sternal region, 

 broadest across the posterior third of its fifth somite ; last 

 segment trefoil-shaped, its sides being slightly emarginate, 

 with its antero-lateral angles slightly covered by the produced 

 postero-lateral angles of the preceding somite. 



The chelipedes are equal and very powerful in the male, sub- 



* Trans. Connecticut Academy, 1870, vol. ii. p. 142, 



I 



