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444 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. > 
Penzus politus, sp. nov. 
Male.—The carapax and abdomen are naked and smooth and the ear- 
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 inconspie- 
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 obseure denti- 
form prominence. 
The eyes are very large, obliquely compressed, and black. The 
peduneles of the antennulz 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 second; 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 expanded 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 exopods to about the middle of 
the carpi of the endopods. The first pair 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 compressed, 
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 suleated 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 
