QUEEN CHARLOTTE ISLANDS. 215 B 



hidentate; beneath it is armed with eight teeth, which extend to the 

 tip. 



CUMACEA. 



Diastylopsis, gen. nov. 



The species for which this genus is proposed is very closely allied to 

 Diastylis in the structure of the appendages of the cephaloperseon and 

 in the structure of the pleon, but it differs from Diastylis, and, as far as 

 I know, from the heretofore described genera of Cumacea, in the con- 

 solidation and great expansion of the tergal and epimeral portions of the 

 third and fourth free segments of the peraeon, which forms an arched 

 shield-like plate nearly half as large as the carapax. The basal seg- 

 ments of the second pair of gnathopods (third maxillipeds) are more 

 expanded distally and form a much more complete oral operculum 

 than in Diastylis. The cephaloperseon, also, is much more elongated 

 and more compressed laterally than in any described species of 

 Diastylis. 



Diastylopsis Daivsoni, sp. nov. 



Female. — The cephaloperseon is considerably longer than the pleon, 

 compressed laterally so that the breadth is little more than a fourth of 

 the length, and the part made up of the free segments is fully as wide 

 and as high as the carapax. The carapax is more than twice as long- 

 as high and smoothly rounded above, though the dorsum is compressed 

 somewhat anteriorly. The eye is obscure or wanting, and the anterior 

 lobes of the carapax extend far in front of the ophthalmic lobe and 

 form a prominent and .acute rostrum. There is a deep antennal sinus 

 (much deeper than in the species of Diastylis) in the anterior margin 

 below the rostrum and bounded inferiorly by the prominent dentiform 

 antero-lateral angle, back of which the lateral margin is dentated for a 

 short distance. The entire surface of the carapax, as well as the dorsal 

 surface of the free segments of the perseon, is perfectly smooth, naked 

 and highly polished, but there are four nearly equidistant, faintly 

 indicated transverse lines crossing the anterior half of the carapax 

 and evidently marking the areolation so conspicuous in some species 

 of Diastylis. The first and second of the five free segments of the 

 peraeon are short and nearly or quite covered each side by the third 

 segment, which is itself short above but greatly expanded each side 

 into a large plate a third as long as the carapax ; the dorsal part of the 

 fourth segment is greatly elongated, and lies between and above the 

 lateral prolongations of the third segment; and the tergal and 

 epimeral portions of these two segments are anchylosed or closely 

 united together, so that the U-shaped suture between them is only 



