42 G. O. SARS. N.-N. Kl. 



and, as in most other species, Hanked liy a thin pellucid border. The 

 posterior extremity appears somewhat broader and blunted. 



Seen from above (fig. 2 1)), the shell exhil)its a regular ovate form, 

 with the greatest width behind the middle. The anterior extremit}^ tapers 

 to an obtuse point, whereas the posterior appears obtusely rounded. 



The «valves are rather thin, semi-pellucid, and but little unequal, 

 though, as in other species, the right one may be found to be slightly 

 larger than the left. The surface of the shell is smooth, clothed with 

 delicate hairs, which are more conspicuous at each extremity, forming, 

 along their edges, a rather dense fringe. 



The eye is large and very conspicuous l)oth in the lateral and dorsal 

 views of the animal. 



The several appendages seem to be constructed much as in the 

 other species of the genus. 



The ground colour of the shell is \\'hitish, with a faint yellowish 

 tinge changing, on the posterior part, to a light orange. But, besides, the 

 shell is variegated with a bluish green pigment arranged in irregular 

 patches and dots, without forming, as in most other species, any pro- 

 nounced transversal bands. 



Observations. Some specimens of this little form, all of them 

 females, were obscrvcfl in one of my aquaria, and continued to Vive 

 during the whole summer. They did not, however, multiply to any 

 great extent, neither did this form reappear the succeeding seasons. In 

 habits it closeh' agrees with the other species of the genus. 



17. Cypridopsis assimilis, G. O. Sars, n. sp. 

 (PI. 6, fig. 3, a— b). 



Specific Characters. Shell rather tumid, being considerably wider 

 than it is high : — seen laterally, of a somewhat semilunar form, with the 

 greatest height about the middle, dorsal margin boldh" cur^'ed, ventral 

 slightly sinuated, both extremities rounded and nearly equal : — seen from 

 above, broadly ovate, greatest width considerably behind the middle, 

 anterior extremity obtusel}^ pointed, posterior broadly rounded. Valves 

 thin, semi-pellucid, and clothed with fine hairs, surface smooth. Colour 

 whitish, with irregular dark-green patches forming 3, partly interrupted 

 transversal bands. Length of adult female 0,68 mm. 



Remarks. This form looks very like the European species C. vidua 

 Müller, but seems to differ in a few points, so that it must rightl)' be 

 regarded as a separate species. 



