Mr. W. Thompson on new species of British Crustacea. 113 



of a rich orange-brown. This Hippolyte in its general appear- 

 ance very nearly approaches H. Cranchii, from which it differs 

 in the form and number of the spines on the rostrum and at the 

 apex, the shape of the rostrum, the shape of the third segment 

 of the abdomen, and some other particulars. 



I have ventured to name this species after Mr. Yarrell, to 

 whose constant friendship, advice and writings, I attribute my 

 partiality to natural history, and whose kindness at a critical 

 age in my youth taught me to turn ray leisure hours to, I hope, 

 a good account. 



Hippolyte Grayana (mihi). Gray's Hippolyte. PL YI. fig. 3. 



Spec. Char. Rostrum (fig. 3 a) long, hollowed out above and 

 below ; above unanued, with the exception of one tooth near the 

 apex ; beneath with three teeth. 



Carapace rather compressed and of a moderate length. 



Rostrum long, the upper edge much hollowed out, and the 

 widest part armed with a tooth a little behind the apex ; this 

 tooth is shorter than the apex, and cuiTcd downwards ; the apex 

 is acuminate, and longer than the upper tooth ; the base of the 

 teeth placed above and beneath the apex are on a line, and as 

 they are both placed on a carina proceeding from the rostrum, it 

 makes that portion verj' deep, and gives it an appearance of a 

 tridentate rostrum. 



The under side of the rosti'um is also much hollowed ; its least 

 depth is immediately over the middle of the peduncle of the eye ; 

 it then gradually deepens "towards the extremity until it attains 

 the greatest depth, when it again turns up, and ends in a tooth 

 just under the apex. It is further armed underneath with a 

 tooth at the point of its greatest depth, and another a little in 

 advance, thus making three teeth on the under side of the 

 rostrum. A sharp tooth is placed over each orbit, and a second 

 on each side of the anterior inferior portion of the carapace. Scale 

 of the external antennse rather narrow, long, extending beyond 

 the filaments of the interaal antennae, w4th a tooth on the 

 outer margin, at about one quarter the length of the scale from 

 the extremity ; the inner margin appears to be toothed or rather 

 notched. 



There is a peculiar process at the end of the scale ; the inner 

 margin ends with a curved spine or cilium, and the outer margin 

 has a straight process against which the crooked one closes. I 

 cannot determine whether they have motion or not. 



Middle plate of the tail slender, tapering, with two pairs of 

 exceedingly minute spiues, only visible with a lens. Abdomen 

 compressed, of even depth as far as the posterior edge of the 



