from the Arctic and Scandinavian Seas. 33 
form of the present, which seems to be a peculiarly Arctic 
species. ‘The points of difference are chiefly these: C. pul- 
chella has a more boldly arched dorsal margin, is considerably 
larger, and its greatest width is placed behind the middle; its 
hinge-teeth are also much better developed; the terminal 
claws of all the feet differ remarkably in their conformation 
from those of C. rubida, and the urticating sete are also of 
different type: it is, mdeed, chiefly this latter character 
which induces me to keep the two species separate. From 
C. villosa it may be distinguished by the colour of the shell, 
its much more delicate punctation and greater tumidity, as 
well as by its less-angular lateral outline. The single spe- 
cimen which obtained C. pulchella a place in my monograph 
of the British Ostracoda was small and probably immature ; 
and as the fine series of specimens obtained by Mr. Crosskey 
from Davis’s Straits afforded an opportunity for a more com- 
plete examination, both of the external and internal charac- 
ters of the species, I have thought it well in this place to 
redescribe it from the Arctic specimens. It may be noted that 
the fossil glacial specimens are somewhat intermediate in cha- 
racter between these and C. rubida. 
Hab. Lat. 67° 17' N., long. 62° 21’ W. Six feet below low- 
water mark. 
Cythere Robertsont, nov. sp. (Pl. IV. figs. 5, 8-10.) 
Shell of the female compressed, subcuneiform, much higher in 
front than behind; greatest height situated at the anterior 
third, and equal to rather more than half the length: ex- 
tremities obliquely rounded; anterior broad, posterior nar- 
rowed : superior margin straight, sloping steeply from before 
backwards ; inferior sinuated in the middle, curving upwards 
behind. Seen from above, compressed, oblong, with nearly 
parallel sides; anterior extremity acuminate, posterior sud- 
denly tapered, obtusely pointed ; width much less than half 
the length. End view ovate, widest in the middle. Shell 
of the male much narrower; surface of the shell covered 
with closely set angular pittings ; colour yellowish. Length 
5 inch. 
This very distinct and pretty little species was dredged by 
Mr. D. Robertson, at Drobak, Christianiafiord, in a depth of 
30-35 fathoms. I have much pleasure in dedicating it to its 
discoverer. 
Cytheropteron vespertilio (Reuss). (Plate V. figs. 6, 7.) 
montrosiense, C. B. & R. (Plate V. figs. 1-5.) 
inflatum, C. B. & R. (Plate V. figs. 8-10.) 
Our knowledge of these species 1s derived chiefly from fossil 
Ann. & Mag. N. Hist. Ser. 4. Vol. ii. 3 ; 
