DECAPOD A. 

 BRACHYURA. 



CORYSTID^E. 



GENUS THIA, LEACH. 



CANCER. Herbst. 



THIA. Leach, Risso, Latr. Edw. 



Generic character. External antennce of moderate length, in- 

 serted beneath the front, just at the inner side of the orbits. 

 Internal antennae, transversely folded beneath the front. External 

 pedipalps extending forwards to the antennal fossa ; the inner 

 branch with second joint shorter than it is broad, its anterior inner 

 angle truncate and submarginate. Orbits extremely small. Eyes 

 scarcely visible. Carapace somewhat heart-shaped, considerably 

 narrowed at the posterior portion, nearly horizontal from before 

 backwards, much arched from side to side ; the front broad, lamel- 

 liform, entire, bounded by a small notch on each side. Anterior 

 legs short, and slightly compressed, the fingers deflexed; the 

 remaining pairs still shorter, each terminating in an acute styli- 

 form joint. Abdomen in both sexes very narrow ; in the male 

 with the three middle joints united ; in the female the seven 

 joints all moveable. 



A GENUS established by Leach, in his " Zoological 

 Miscellany," on a species of which he was ignorant of the 

 locality. 



