PETALOPHTHALMUS PACIFICUS. 223 
= 
comes necessary to modify Sars’s diagnosis of the genus Pelalophthalmus * as 
follows : — 
Sexes similar. Carapace short, leaving the last two thoracic segments 
exposed. Kye-stalks leaf-like, without any visual elements or pigment. An- 
tennular peduncle greatly elongated in both sexes, and without the usual © 
hirsute lobe in the male. Antennal flagellum small, antennal scale lanceo- 
late or narrowly oval, setose on both margins. Mandibular palps prodigiously 
developed in both sexes, forming powerful prehensile organs. Maxillipeds 
devoid of exopods, but furnished with well developed epipods; meral seg- 
ment expanded interiorly so as to form a large linguiform lobe. Gnatho- 
pods (or first pair of legs) short, strong, subcheliform, devoid of exopods; 
meral segment expanded on the inner side to form a very large, porrect 
lobe. Terminal segment of fourth pair of legs (counting the gnathopods as 
the first) obtuse and densely hirsute. Caudal limbs scarcely natatory even 
in the male. Marsupial pouch of female composed of seven pairs of incu- 
batory lamella, the anterior pair rudimentary. Apex of telson entire, not 
incised in the middle. Outer plates of the uropods distinctly jointed near 
the apex. 
In the “ Challenger” specimen of P. avmager, the second and third pairs of 
legs were imperfect, lacking all the joints of the endopods beyond the point 
of articulation with the exopods. It is remarkable that these same joints are 
lost from the same appendages both in the “ Albatross” specimen of P. paci- 
ficus and in the P. armiger obtained during the cruise of the “ Blake.” 
Petalophthalmus pacificus Fax. 
Plate LIV. 
Bull. Mus. Comp. Zodl., XXIV. 218, 1893. 
Similar to P. armiger W.-Suhm, but different in some particulars. The 
rostrum is more prominent, and there is a median tooth on the carapace be- 
hind the rostrum. The caudal limbs of the male are quite different from 
those of P. amiger as described and figured by G. O. Sars. In the latter 
each pair of caudal limbs bears a slender cylindrical external branch, whilst 
in P. pacificus the first pair is wholly destitute of an external branch, and the 
second pair (Plate LIV., Fig. 12) discloses but the slightest rudiment of such 
a branch in the shape of a minute bud barely discernible with the aid of 
* Op. cit., p. 173. 
