282 



ALPHEADA;. 



ing pairs are slender and simple. The abdomen is evenly 

 rounded and smooth. The outer plate of the tail trans- 

 versely divided about one-third from the extremity. In its 

 general aspect it resembles a very young Astacus. 



The length of Dr. Leach's specimens is rather more than 

 half an inch. 



Colour light buff ? 



The discovery of this species is due to Montagu, who 

 sent it to Dr. Leach, under the name of " Cancer (Astacus) 

 nitescens? The latter author states that "it is occasion- 

 ally found in pools left by the tide amongst the rocks on 

 the coasts of Devon and Corn wall." It cannot, however, 

 be otherwise than rare in that locality, as Mr. Couch does 

 not introduce it in his " Cornish Fauna." Mr .W. Thomp- 

 son thus records its occurrence on the Irish coast : " A 

 single specimen was found under a stone, between tide- 

 marks, at Lahinch, county Clare, by Mr. E. Forbes and 

 myself, in July, 1 840." These are the only authentic notices 

 of its existence on the British islands that I am acquainted 

 with. Dr. Milne-Edwards mentions its inhabiting the 

 coast of France, but gives no particulars. 



The following figure represents one of a series of speci- 

 mens in the British Museum collection, from Plymouth 

 Sound, remarkable for the large size of the first leg on the 

 right hand side of the body. 



