MUSEUM OF COMPARATIVE ZOOLOGY. 



Pontophilus brevirostris Smith. 

 Proc. National Mus., Washington, III. p. 435, 1881. 

 Plate VII. Figs. 1 - 1". 



This species is very closely allied to P. spinosus and P. Norvegicus, but is 

 readily distinguished from them by the very short rostrum, which is triden- 

 tate, with the median tooth scarcely broader and very little longer than the 

 lateral, about reaching to the cornea of the inner side of the eye and not pro- 

 jecting beyond the line of the spiniform outer angles of tlie orbits. The pro- 

 portions of the body are more like spiiiosus than Norvegicus, but the carination 

 and armature of the carapax are more like Norvegicus, while the sculpture of 

 the distal somites of the abdomen is more like spinosus. 



The dorsal carina of the carapax is armed with three spines, and frequently 

 a smaller fourth one in front of the others and just back of the base of the 

 rostrum ; the subdorsal carina is armed with two spines, as in Norvegicus, and 

 often with a rudiment of a third behind these ; the lateral carina does not 

 extend back of the middle of the carapax, and is armed with a single spine, as 

 in Norvegicus. There are no distinct carinse on the first four somites of the 

 abdomen, but the fifth somite is flattened above and has subdorsal carinas 

 slightly diverging posteriorly, and below these, each side, another carina, 

 nearly parallel with the subdorsal ; and the sixth sonn'te is flattened above and 

 subdorsally carinated, as in spinosus, though the cariuai are not quite as con- 

 spicuous on either somite as in that species. 



The eyes, antennulae, and antennae are very nearly as in P. spinosus. The 

 external maxillipeds reach a little beyond the tips of the chelipeds, the penulti- 

 mate segment reaches nearly to the tip of the antennal scale, rnd the ultimate 

 segment is a little less than twice as long as the penultimate, while in P. Nor- 

 vegicus it is about once and a half as long, and in P. spinosus much more than 

 twice as long, as the penultimate segment. The thoracic legs difl'er scarcely at 

 all from those of P. spinosus. 



The lamellae of the uropods are very nearly as in P. spinosus. The inner 

 lamella reaches nearly or quite to the tip of the telson, is lanceolate, and six or 

 seven times as long as broad ; the outer lamella is about a tenth shorter than 

 the inner, and about four times as long as broad. The telson is once and a 

 fourth to once and two fifths as long as the sixth somite of the abdomen, is very 

 narrow, slightly acuminate, and has a very narrow and acutely triangular tip, 



