TRIDENS. 



281 



1SOPODA. 



NORMAL1A. 



TRIDENS. 



Specific character. Differs from ^Ega bicarinata in having the last seg- 

 ment of the tail furnished with three carinae, each of which is produced into 

 a small point beyond the posterior margin of the segment, the space between 

 the two lateral teeth being emarginate ; eyes large, having only a small space 

 between them in the centre of the anterior margin ; inner plate of the caudal 

 appendages larger than the outer and truncated at its extremity. 



Length, an inch and a half. 



sEya tridens. LEACH, Trans. Linn. Soc. xi. p. 370. Die. Sc. Nat. xii. 



p. 349. DESMAREST, Crust, p. 305. MILNE EDWARDS, 



Crust, iii. p. 242. WHITE, B. M. Cat. Brit. Crust. 



p. 80. Pop. Hist. Brit. Crust, p. 251. 

 Var. ? with central spine of tail obsolete. ^Ega monoplithalma var. minor. 



JOHNSTON, in London's Mag. Nat. Hist. vii. p. 233, 



fig. C. (?) 



THIS species is closely allied 4;o jEga bicarinata, but is 

 distinguished by the three carinae on the terminal segment 

 of the tail, the two lateral ones being the strongest, and 

 each terminating in a small tooth on the posterior edge of 



