444 PEOCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



Penaeus politus, sp. nov. 



Male. — The carapax and abdomen are naked and smooth and the car- 

 apax is armed with well-developed antennal, hepatic, and branchiostegial 

 spines, but the sulci are all shallow and indistinct. The rostrum is short, 

 acute, about two-fifths as long as the rest of the carapax, scarcely over- 

 reaches the eyes, rises obliquely from the anterior part of the carapax, 

 and then points straight forward ; its dorsal crest is armed with seven 

 or eight teeth, of which the posterior one is just back of the orbit, while 

 the two or three most anterior ones near the tip are small or inconspic- 

 uous and nearer together than toward the base ; the lower edge is cil- 

 iated and minutely multidentate, the teeth being slender, acute, and 

 closely crowded, so that, to the naked eye, the edge appears entire. The 

 dorsal crest extends nearly the whole length of the carapax, but grad- 

 ually fades out posteriorly, and, at about a third of the way from the base 

 of the rostrum to the posterior border, rises into a low and obscure denti- 

 form prominence. 



The eyes are very large, obliquely compressed, and black. The 

 peduncles of the antennulae reach to the tips of the antennal scales; 

 the lamelliform appendages of the basal segments are small, narrow, 

 and do not cover the eyes above, but lie concealed between the eye- 

 stalks ; the second segments are slightly longer than the basal, while 

 the third are not quite half as long as the secoud ; the inner flagellum 

 is about as long as the carapax, including the rostrum, and tapers regu- 

 larly throughout its length; the outer flagellum is slightly shorter than 

 the inner, and suddenly exj)andod toward the base, but the terminal 

 portion more slender than in the inner flagellum. The antennal scales 

 are about twice as long as the rostrum, rather more than a fourth as 

 wide as long, and taper regularly to the broadly rounded tips. The 

 terminal segment of the peduncle of the antenna is scarcely a fourth as 

 long as the antennal scale, and the flagellum is slender and much longer 

 than the whole body. 



The external maxillipeds are slender, and reach a little beyond the 

 middle of the antennal scale, and their exoi>ods to about the middle of 

 the carpi of the endopods. The first i)air of legs reach only to the mid- 

 dle of the carpi of the external maxillipeds, the second pair to near the 

 middle of the propodi, and the third and fourth pairs to the tips of the 

 external maxillipeds, and the fifth a little beyond the tips of the fourth 

 pair. The dactyli of the fourth and fifth pairs are slightly comj)ressed, 

 and only about half as long as the propodi. 



The first, second, and third abdominal somites are rounded above, 

 but the fourth, fifth, and sixth are compressed and sharply carinated 

 dorsally. The sixth somite is very much compressed, longer than the 

 fourth and fifth taken together, and about twice as long as high. The 

 telson is shorter than the sixth somite, dorsally sulcated with the mar- 

 gins of the sulcus terminating posteriorly in a long spine either side of 

 the tip, which is itself imperfect in the single specimen seen. The outer 



