REPORT ON THE CRUSTACEA MACRURA. 415 



Observations. — The specimen from the New Hebrides, which I have selected as belong- 

 ing to this species, differs from Kroyer's description in having a small tooth or tubercle on 

 the dorsal surface of the third somite of the pleon ; in all other respects it corresponds 

 very closely, and is probably a young one, or one not yet fully developed. 



Sergestes longirostris, n. sp. (PI. LXXV. fig. 3). 



Rostrum long, slender, directed horizontally forwards in a line with the dorsal surface 

 of the carapace, of which it is rather more than one-half the length. Carapace, not 

 including the rostrum, about one-third of the length of the animal. 



Pleon having the five anterior somites subequal, the three anterior dorsally smooth, 

 and with the postero-lateral margins round ; the succeeding two somites are dorsally 

 armed with a tooth at the posterior margin, and the postero-lateral margin is also produced 

 to a point, of which that of the posterior is the more prominent ; the sixth somite is 

 about equal in length to the three preceding somites united, and is dorsally furnished 

 with a tooth at the posterior margin. 



The telson is about half the length of the rhipidura, terminates in a forked extremity, 

 and has on each side a small hair or spine. 



The ophthalmopoda are long, reaching to the extremity of the second joiut of the 

 first pair of antennae and passing beyond the extremity of the rostrum by the breadth of 

 the ophthalmus, which is broader than the stalk, and gives the organ a clavate appearance. 

 The first pair of antennae has the first joint the longest, the second a little shorter 

 than the first, and the third a little shorter than the second. The long flagellum is 

 wanting in our typical specimen, and the secondary branch is very rudimentary. 



The second pair of antennae ha3 the flagellum also wanting, but the scaphocerite is 

 long and narrow, as long as the ophthalmopod, has the margins parallel, and terminates in a 

 rounded extremity, the outer margin being armed with a long tooth that is situated at 

 some little distance from the extremity, and the inner margin fringed with long ciliated 

 hairs. 



The oral appendages have not been examined. 



The first pair of gnathopoda is the only appendage belonging to the pereion that is 

 preserved, and it exhibits no character of any specific value. 



The pleopoda are moderately long and slender ; the first pair being the most so, and 

 the fifth pair the stoutest and most robust. The first pair is simple, the second and 

 three following carry a small secondary ramus that becomes smaller in each succeeding 

 pair, and is almost a rudimentary bud on the fifth pair. The sixth pair, forming the 

 outer plates of the rhipidura, has the outer margin armed with a strong tooth near the 

 middle, beyond which it is fringed with ciliated hairs, which are also present on the inner 

 margin and on both margins of the inner plate. 



