DECAPOD A. MAIADM. 



RRACHYURA. 



GENUS HYAS, LEACH. 



CANCER, Hcrbst. 



MAIA, Bosc. 



INACHUS, Fabricius. 



PISA, Latr. 



HYAS, Luacli, Edwards. 



Generic character. External antennae with the basal portion 

 slightly narrowed forwards, and separated from the outer portion 

 of the orbit by a notch ; the second joint dilated externally, longer 

 than the third. External pedipalps with the third joint notched 

 at the internal apex. The first pair of legs thicker than the rest, 

 shorter than the second pair, and equal ; the fingers tapering to 

 the point, and when closed, meeting throughout nearly their whole 

 length. The remaining pairs of legs simple, slender, long, almost 

 cylindrical ; the terminal joint without spines beneath. Carapace 

 tuberculous,, elongate- subtriangular, much rounder at the posterior 

 margin ; rostrum of moderate length, triangular, depressed ; the 

 lacinia: somewhat converging. The lateral margin with a strong 

 spear-shaped process immediately behind the orbit. Eyes capable 

 of being deflexed within the orbits. Abdomen seven-jointed in 

 both sexes ; the terminal joint in the male is transversely oval, 

 and the corresponding margin of the penultimate joint is broadly 

 emarginate to receive it. 



This genus bears considerable relation to Pisa, from 

 which it differs, amongst other characters, in the dilated 

 form of the second joint of the antennae, and the absence of 

 spines beneath the last joint of the legs. 



