122 



Of this subgenus there are two species, as is shown in the following table : — 



I. Fi'ont square-cut, its width little more than the maximum diameter 

 of the orbit, and about one-sixth the greatest breadth of the cara])ace ; 

 finger-cleft and inner surface of palm naked .... G.jacqiiemontii. 

 II. Front with convergent sides, its width exceeds the maximum 

 diameter of the orbit by one-fourth, and is about one-fifth the greatest 

 breadth of the carapace ; finger-cleft and neighbourhood of inner 

 surface of palm concealed in a thick, shaggy mat of hair . . G. eduardsi, 



1. Ctecarcinucus (Gecarcinucus) jacquemontii, Edw. (Fig. 66.) 



Gecarciiiiiciisj'aajuemontii, Milne Edwards in Jacquemont's Voy. dans Plnde, IV., Crust., p. 4, pi. i., 1844 ; 

 Mary .J. Rathbun, Nouv. Archiv. du Museum (4), VIII., 1906, p. 67, pi. xix., figs. 1, 2 {iibi lit.). 



Carapace convex, subcylindrical, its depth considerably over half its length, 

 broadly oval, its length hardly two-thirds its greatest l)readth ; its surface and 

 side-walls practically smooth to the naked eye. 



" Cervical " groove very broad and deep, running in a long, narrow, 

 markedly antero-posterior loop. 



Regions of carapace very clearly defined, individually tumid ; post-frontal 

 mesogastric groove long ; a distinct tumid oval facet in the cardiac corner of 

 either epibranchial region, and between them two smaller, less distinct, prse- 

 cardiac facets. 



Front, in the adult, a long, narrow^ square- cut, vertically-deflexed lobe, 

 not or hardly wider than the orbit ; broadly bilobed in a dorsal view, and with 

 a somewhat bilolied surface owing to the faint anterior prolongation of the 

 mesogastric groove. 



As the anterior part of the carapace is deflexed, very little is seen of the 

 orbits in a dorsal view; they are wide, and have a thick, .smooth, lip-like 

 margin, which is broken only by the wide antennal gap ; their lower border is 

 so bent as to form a large bight in the orbital cavity at its lower outer corner : 

 the external orbital angle is quite sujDpressed. 



Antero-lateral borders of carapace strongly arched, longer than the postero- 

 lateral, with a tumid margin which, however, in its front part, is defined by a 

 low, thick, obscurely-crenulate edge. There is no trace of an epibranchial 

 tooth, the sweep of the antero-lateral margin being hardly broken where the 

 cervical groove meets it. 



Epigastric crests low, blunt, obscm-e, continuous on either side of the 

 mesogastric groove with the still blunter and more obscm-e post-orbital crests ; 

 the latter are approximated to the orbit and follow its curve, but can seldom be 

 traced beyond the cervical groove. 



Abdomen of adult male fairly regularly and narrowly triangular ; in the 

 6th segment the sides converge, and the length exceeds the di.stal breadth ; the 

 7th segment is tongue-shaped, and its maximum breadth is not two-thirds its 



