28 G. O. Sars. 
The adult male (fig. 3) is of somewhat smaller size 
than the female, scarcely exceeding a length of 1.20 mm. 
and has the shell comparatively shorter, with the dorsal 
margin still more boldly curved. It may, moreover, at once 
be recognized by the darker brownish colour, and by the 
spermatic vessels shining more or less distinctly through 
the shell. These vessels are arranged in exactly the same 
manner as in the male of C. dentato-marginatus, forming 
in the posterior part of each valve 4 densely crowded coils, 
whereas a single vessel is sent off in front, and runs along 
the anterior extremity. 
The palps of the posterior maxille are, as is usual in 
male specimens, transformed into strong grasping organs, and 
resemble in shape those in the above-numed species, being 
rather dissimilar on the two sides. The outer sexual append- 
ages (fig. 5) have also much the same appearance as in that 
species, 
Biological Observations. 
This beautiful species, which I have much pleasure in 
dedicating to Mr. Knut Dahl, to whom I am indebted for its 
examination, developed in great abundance in some of my 
aquaria, and has been watched in several successive gener- 
ations, At first, however, only some few specimens, males 
and females, appeared in each of the aquaria; but these 
rapidly multiplied, and at last gave rise to a vast progeny. 
At the time when this is written (in the beginning of Octo- 
ber), the aquaria still swarm with this Ostracod, and it is 
my intention to keep them for subsequent observation. 
As to habits, it is a very active animal, swimming 
about with great speed by the aid of the long natatory sete 
issuing from both pairs of antenne. Especially during the 
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