416 



REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



[72] 



tiarticulate, as in the two following species, but the articulations are- 

 more conspicuous. These structural characters of the peraeopods are^ 

 however, undoubtedly characteristic of all the species of the genus. 



Sergestes robustus Smith. 



Sergcstes, sjh, Smith, Proc. National Miis., iii, p. 445, 1881. Sergestes robusius 

 Smith, Bull. Mus. Comp. Zool., s, p. 97, pi. 16, figs. 5-8b, 1882. 

 (Plate 8, Figs. 3-6 &.) 



Specimens examined. 



Male. — The carapax is strongly compressed, the breadth being con- 

 siderably more than the height at the base of the antennae, but much 

 less that! the greatest height posteriorly, which is fully twice that at the 

 base of the antennae. The dorsum is broadly rounded to the base of the 

 rostrum, which rises rather abruptly from the dorsum, is very thin, 

 acutely triangular, and extends a little forward of the truncated middle 

 lobe of the ophthalmic somite. 



The eye-stalks to the tips of the eyes are about two-fifths as long as the 

 antennal scales, and the diameter of the eye itself at leasthalf the length. 

 The peduncle of the antennula is fully a fourth longer than the antennal 

 scale, the first segment scarcely half as long as the antennal scale, and 

 the second and third successively^ a little shorter; all the segments are 

 very stout, the diameter in the second and third being equal to more 

 than half the length. The proximal segment of the upper or major fiagel- 

 him is scarcely more than a fourth as long as the distal segment of the 

 peduncle, and scarcely longer than the i)roximal segment of the Hagel- 

 lum, which is modified as in the allied species. The antennal scale (Fig. 

 5) is about half as loug as the carapax along the dorsal line, about a 

 third as broad as long, and much broader at the tip than in the allied 

 species. 



The oral appendages do not differ essentially from the oral append- 

 ages of P. Frisii and arcticus as figured by Kroyer. 



The second gnathopods reach by the tips of the antennal scales fully the 

 length of their dactyli, and are about as stout as the third perseopods: 

 all five segmeuts of the endopod are approximately equal in length, 

 though the dactylus is slightly shorter than the others, and all are 

 armed with very slender spines ; the dactylus is slender and multiar- 

 ticulate, being composed of about five segments, and tipi)ed with two 

 or three spines. The first peneopods fall a little short of the tips of the 



