DECAPODA. ORTUNIDJL. 



BRACHYURA. 



GENUS PORTUMNUS. 



CANCER, (LATIFES), Planci. 



CANCER, Pennant, Herbst. 



PORTUMNUS, Leach. 



PLATYONYCHUS, Latr. Edwards. 



Generic Character. External antennce inserted at the inner 

 canthus of the orbit, the basal joint small, not united to the front, 

 moveable. Internal antennte lying obliquely in their fossa?, which 

 are but incompletely separated from the orbits. External pedi- 

 palps extending forwards to the antennary fossse ; the third joint 

 elongated, emarginate at the inner margin a little behind the 

 apex, for the articulation of the palpal portion, which is three- 

 jointed. Anterior feet sub-compressed, equal ; second, third, and 

 fourth pairs with the terminal joint compressed, narrow, lanceo- 

 late, that of the first rather broader ; the fifth pair with the 

 penultimate joint broad, rounded, and compressed, the terminal 

 acutely lanceolate, and broader than that of the other pairs. Cara- 

 pace, as long as it is broad ; front, narrow, toothed ; latero- 

 anterior margin arched ; the posterior half of the carapace gradu- 

 ally narrowed ; posterior margin truncate. Orbils, with the upper 

 margin evenly concave, and with a single fissure, the inner canthus 

 open. Eyes, not larger than their footstalks, which are rather 

 slender and slightly curved. Abdomen, in the male, five-jointed, 

 the third and fourth joints much longer than they are broad, the 

 third being the longest ; in the female, seven-jointed, less than 

 half as broad as it is long, the second, third, and fourth joints 

 very short, the fifth transversely quadrate, the sixth and seventh 

 regularly diminishing to the apex. 



