234 THALASSINAD.E. 



terminate each in a small spine above the orgriu of the 

 moveable finger. The second pair of feet is distinctly 

 and evenly didactyle, resembling in general form the 

 first pair, but very much smaller ; and the remaining 

 pairs are very slender, and monodactyle. The whole of the 

 feet, as well as most of the limbs and other appendages, 

 are hairy. The abdomen is shorter in proportion, and less 

 cylindrical, than in some other of the fossorial forms. 



The general colour is a delicate pink or pale rose, 

 varying in depth in different parts ; but it soon becomes 

 white after being placed in spirit. 



The total length is about two inches. 



This species constitutes one of the most singular and 

 interesting additions which have, for a long time past, 

 been made to our list of British Crustacea. Allied as it is 

 in its essential characters to the Thalassinada in general, it 

 exhibits some points of structure so abnormal, that at the 

 first examination it would scarcely be recognized as belong- 

 ing to that group. Instead of the thick and clumsy 

 hands, the imperfect claws, and the short, solid form of 

 the other limbs, which are exhibited in Gebia and Callia- 

 nassa, we see in this species a remarkable degree of slender- 

 ness in the limbs, and an almost normal structure of the 

 hands, assimilating it in some degree to the ordinary 

 Paleetnonida or Astac'idte. The absence of all colouring 

 pigment, as well as of the cornea: in the eyes is a very 

 remarkable, and, as 1 believe, an unique instance in the 

 whole of the higher forms of Crustacea. But it is ad- 

 mirably in keeping with its habits, as will be presently 

 seen . 



In a fine collection of Irish Crustacea, made by my friend 

 Mr. W. Thompson, and obligingly lent to me by him 

 some three years since, there occurred a pair of the 



