226 THALASSINAD.E. 



figure,* not more than half the length of the body. The 

 abdomen is broader, more spread, and much less firm in 

 its texture, the sides being almost membranaceous, and 

 the abdominal false feet larger and more voluminous than 

 in the other species. The different lamellae of the tail 

 differ also in some particulars, the exterior being rather 

 broader than it is long, and the middle one, or terminal 

 segment of the abdomen, nearly quadrate. ( In all other 

 respects the two species very greatly resemble each 

 other. 



Whether the distinctions above enumerated constitute 

 anything more than sexual characters, I cannot at present 

 determine, nor have I hitherto had access to a sufficient 

 number of specimens to enable me to make a satisfactory 

 comparison ; but I confess I am very doubtful if it will 

 not prove, upon further investigation, that the two British 

 forms, and perhaps also G. littoralis of Risso, constitute 

 but one species. The form and development of the abdo- 

 men, and the great volume of the abdominal false feet 

 in G. deltura, are certainly very much like peculiarities 

 belonging to the female sex, and calculated for the support 

 and protection of the ova. " This species," says Dr. 

 Leach, " lives with G. stellata, with which it was con- 

 founded until the distinctions were discovered by Mr. 

 J. D. 0. Sowerby." 



* In the only specimens I have seen, which are those in the British Museum, 

 the antennae are somewhat injured. 



*h The term " deltoid " appears to be very much misplaced in describing this 

 part. 



