78 A HISTORY OF KECENT CRUSTACEA 



CHAPTER VII 



TRIBE II. — CATOMETOPA 



The 'front' is bent downward. The carapace is broad 

 anteriorly, often subquadrate, sometimes subglobose, trun- 

 cate or arcuate forwards, but not rostrate. The epistome 

 is short, often almost linear. The pairs of branchiae are 

 usually fewer than nine in number ; the efferent channels 

 open at the sides of the endostome. The third maxilli- 

 peds have the fifth joint articulated at the front outer 

 angle of the fourth, or less frequently at its apex, or very 

 rarely at the front inner angle. The male verges are 

 inserted either in the sternal plastron, or in the basal 

 joints of the last pair of legs, thence passing through 

 channels in the sternum beneath, tlie pleon. 



The tribe contains four families, the Gecarcinidae, 

 Ocypodidae, Grapsid^, and Pinnotheridae. The liver is 

 said by Milne-Edwards to be in general central, extend- 

 insr little or not at all over the branchial cavities. 



o 



Family 1 . — Oectwcinidce. 



The carapace is dorsally very convex, especially dilated 

 over and in front of the branchial regions, with the autero- 

 lateral margins usually entire and strongly arcuate. The 

 ' front ' is of moderate width and strongly deflexed. The 

 orbits and eye-stalks are of moderate size. The third 

 maxillipeds have the fifth joint articulated at the front 

 outer or near the front inner angle or at the apex of the 

 fourth, which sometimes completely conceals it. The 

 chelipeds in the adult male are powerful, usually unequal. 

 The seventh joint in the walking legs is nearly always 



