HYAS COARCTATUS. 



35 



DECAPOD A. 



BRACHYURA. 



MAIADJE. 



Hyas coarctatus. Leach. 



-fie diaracler. Carapace distinctly contracted immediately behind the post- 

 orbitar process. 



Hyas axirctutua, LEACH, Trans. Linn. Soc. XI. p. 329. Id. Malac. Brit. t. 



xxi. B. EDW. Hist. Crust. I. p. 312. COUCH, Cornish 

 Fauna, p. 66. 



Tins is a small and elegant species, differing so much in 

 the contour of the shell from Hyas araneus, as to be dis- 

 tinguished at a glance from that species, although agreeing 

 with it in almost all the essential characters. The carapace 

 is very broad anteriorly, and suddenly contracted at the 

 sides, both of which characters arise from the extraordinary 

 breadth of the post-orbitar processes, which are half lyre- 

 shaped and lamelliform. The rostrum is bifid, triangular, 

 and each lacinia has a series of minute tubercles along the 

 middle. The whole carapace is tuberculated. The an- 

 tennae, the eyes, the orbits, and the pedipalps, are very 



D 2 



