404 CRUSTACEA. 



The occurrence of a very large specimen of a new species of 

 Alauna in Sir Edward Belcher's collection has afforded to Mr. 

 Westwood an opportunity of figuring, for the present Paper, 

 the details of the anatomy of all the essential parts, a task 

 which, as a reference to the figures will show, he has executed 

 with his usual unrivalled accuracy and tact. These details 

 appear to confirm the opinion that this family must be placed 

 amongst the lower forms of the decapodous group. The num- 

 ber and general structure of the parts connected with the office 

 of manducation, and of the thoracic feet, are entirely consis- 

 tent with this view ; and the structure of the tail, which is 

 formed of the appendages to the sixth abdominal segment 

 and of the seventh, no less agrees with it. The absence 

 of any ocular peduncle however shows an aberration from the 

 type, of such importance as to throw a strong apparent doubt 

 upon the subject. Besides the single large specimen, there 

 are several others in the collection considerably smaller (fig. 

 3), which differ in some characters, as the less convex form 

 of the carapace, more obvious rugse on the fore part of it, and 

 the existence of an acute point on each side of the last leg- 

 bearing segment. These may be immature individuals, or 

 possibly males, or they may perhaps be specifically different. 



Hab. Wellington Channel, in thirty-five to seventy fathoms. 



STOMOPODA. 



A single specimen of a Mysis, probably M . Fabricii, was in 

 too decomposed a condition to be identified with certainty. 



AMPHIPODA. 

 GAMMARUS SABINI (Leach). 



Gammarus Sabinl, Leach, in Eoss's Voyage, ii. p. 178; Sabine, 

 Parry's Voyage, Append., p. ccxxxiii. ; Kroyer, Ampliip., p. 16. 

 t. i. f. 3 ; Edw., 1. c. iii. p. 50. 



