1885.] PROCEEDINGS OF UNITED STATP^S NATIONAL MflSEUM. 178 



diameter being nearly half the length of the anteuntil scale, and fiom 

 a third to fully two-fifths of the length of the carapax excluding the 

 rostrum. 



The proximal segment of the peduncle of the antennula is about half 

 as long as the antennal scale, very broad, lamellar, slightly concave 

 above to fit the eye, and the outer margin armed with a small tooth 

 near the base and with a slender spine at the anterior angle ; the sec- 

 ond segment is scarcely a third as long as the proximal and nearly as 

 broad as long; and the distal segment is fully as long as the second, 

 slender and subcylindrical. The antennular flagella are slender, the 

 inner approximately as long as the antennal scale, the outer slijihtly 

 shorter. The antennal scale is considerably broader at base and more 

 tapered distally than in P. longirostris, but otherwise the autenute are 

 nearly as in that sjiecies. 



The perseopods are very similar to those of P. lonfjirosfris, but are all 

 somewhat longer and apparently stouter; the second i)air reach nearly 

 to the second segment of the peduncle of the antennula, and the third 

 and fifth to or a little by the tips of the antennal scales. 



The anterior somites of the pleon are nearly as in P. longirostris, but 

 the dorsal carina on the third, fourth, and fifth is not quite as thin and 

 does not project in so distinct teeth at the posterior margins of the so- 

 mites, and the pleura of the fifth somite project slightly more poste- 

 riorly. 



The telson is a little longer than the sixth somite, conspicuously sul- 

 cated above, the margins of the sulcus carinated and terminating in a 

 long spiniform process either side and a little way from the slender and 

 acute tip. Below the dorsal carina there is an inconspicuous lateral ca- 

 rina either side joining the dorsal a little way from the base of the lateral 

 l^rocess, in front of which there are two aculei on the edge itself. The 

 inner lamella of the uropod reaches to about the tip of the telson, is 

 ovate-lanceolate and between three and four times as long as broad. The 

 outer lamella is considerably longer than the telson, about a fourth as 

 broad as long, with the outer margin terminating, about two-thirds of 

 the way from the base to the tip, in a small spine, beyond which the la- 

 mella is suddenly narrowed but the tip itself rounded. 



The peculiar sexual appendage of the first pleopod is an elongated, ap- 

 proximately rectangular plate longitudinally plicated, and joining its 

 fellow of the opposite side for nearly the whole length of the mesial 

 edge. 



