39 G. O. Sars. 
The natatory setæ on the antenne are very long and 
finely plumose, those of the inferior antenne reaching con- 
siderably beyond the terminal claws. The oral parts and 
the legs are of normal structure, nearly agreeing with those 
parts in the other species of the genus Cypris (sens. strict.). 
The caudal rami (fig. 9) are not particularly large, and 
exhibit at the base a very pronounced curve. ‘They have 
the dorsal edge quite smooth, and carry at the end the 2 
usual claws and 2 small bristles, the one apical, the other 
dorsal. The claws are perfectly smooth, the outer one 
being, as usual, the larger, though scarcely exceeding half 
the length of the ramus. 
In the living state of the animal, the shell exhibits a 
light yellowish colour, with a very conspicuous dark brown 
patch in the dorsal part of each valve, above the insertion 
for the adductor muscle. This patch is generally drawn out 
behind into 2 narrow diagonal bands, the lower of which 
has a somewhat lighter reddish brown colour, and occurs 
just above the cecal appendage of the intestine, whereas 
the upper one lies near the dorsal face. Between the two, a 
pale orange tinge may be observed, caused by the ripe ova 
accumulated within the body. In the region of the eye the 
shell is generally tinged with light chestnut. The cecal 
appendages of the intestine shine through the shell with a 
bluish green colour. 
The adult male (fig. 8) is somewhat smaller than the 
female, scarcely exceeding a length of 1.6 mm, and it slightly 
differs in the shape of the shell. In a lateral view, the 
latter appears comparatively shorter in proportion to its 
height, and less narrowed behind. The dorsal margin is 
less regularly curved, being almost straight in the middle, 
and exhibiting a slight indication to an angle in front and 
