28 
W. M. TATTERSALL. 
narrower, rectangular in shape, outer margin unarmed, inner margin beset with a few 
plumose setse. 
Antennal peduncle (Fig. l) equal in length to the antennular, but more slender; 
last two joints subequal in length. 
Antennal scale (Fig. l) slightly longer than the last segment of the pleon and 
twice as long as the antennular peduncle, about three and a half times as long as 
broad, outer margin entire and terminating in a very strong spine, beyond which the 
apex of the scale is but slightly produced; spine on the basal joint short and acute. 
Mouth parts (Figs. 2, 3, 4, and 5) exhibit no salient points of difference from 
those of the type species of the genus P. roseum, G. 0. Sars. 
First and second thoracic limbs (Figs. 6 and 7) agreeing in the main with those 
figured by Sars for P. roseum, but a dactylus is distinctly visible among the dense 
mass of plumose sct;e arming the terminal joints, though it is smaller and shorter 
than the terminal joint; exopods having the outer distal corner of the basal joint 
round, though produced, and the flagelliform part composed of ten to twelve joints. 
Telson (Fig. 8) slightly shorter than the last segment of the pleon, tapering to 
an evenly rounded apex which is one-third as wide as the base; apex armed with a 
median pair of plumose setrn and four pairs of strong smooth spines, the innermost 
and largest of which equals one-sixth of the telson in length ; distal half of the lateral 
margins armed with five shorter spines. 
Inner uropods half as long again as the telson, armed with a single long spine 
in the region of the inner posterior corner of the otocyst. 
Outer uropods about twice as long as the telson. 
Length of an immature female, 23 mm. By an error the specimen was described 
in the preliminary report as adult. This is scarcely correct, since the incubatory 
lamellae are still only about half developed, so that the adult female probably reaches 
to nearly 30 mm. The specimen is badly mutilated, the third to the eighth thoracic 
limbs being entirely absent. 
P. belgicce is far and away the largest species of the genus yet described, none 
of the other ten known species exceeding 15 mm., whereas adult specimens of this 
species must reach to nearly 30 mm. It is most nearly related to P. sarsi Will.- 
Sulim, described by Sars (1885) from the ‘Challenger’ collections for specimens taken 
at Kerguelen Island. Besides the great difference in size (P. sarsi measures only 
14 mm., adult specimens), the only other conspicuous difference is in the ocular 
laminae. In P. sarsi the antero-lateral angles of the eye-plates are serrate, whereas 
in P. belgicce they are quite smooth. Minor differences in the shape of the antennal 
scale and telson may also be noted. The antennal scale in P. sarsi has the spine 
terminating the outer margin less strong than in P. belgicce, while the apex of the 
scale is more produced. The telson in P. sarsi has the apex more truncate than 
P. belgicce and the lateral margins, according to Sars, bear eight short spines. 
Mr. Holt, however, who has kindly examined the types of P. sarsi in the British 
