34 fe- ö. SARS. M.-N. Kl. 



parentl}^ owing to the aquarium not b^eing suitably arranged, only 2 or 

 3 specimens having been secured for closer examination. 



13. Cypris aurea., G. O. Sars, n. sp. 

 (PI. 5, fig. 4a-c.) 



Specific Characters. Shell rather compressed and but sparingly 

 hairy at each extremity : — seen laterally, oval reniform, nearh' of same 

 height anteriorly and posteriorly, dorsal margin slightly cur\'ed, ventral 

 nearly straight, anterior extremity evenly rounded, posterior somewhat 

 blunted, and, in female, having, above, a slight sinus : — seen dorsall}^ oblong 

 cuneiform, anterior extremity considerably narrower, and terminating in a 

 somewhat twisted, rostriform point, posterior more obtuse. \"alves very 

 unequal, the left one being much the larger, and considerably overlapping 

 the right at each extremity; edges of the latter distinctly crenulated both 

 anteriorly and posteriorly. Surlace of shell smooth, polished. Caudal 

 rami comparatively small, sublinear, claws not very elongated. Colour in 

 female, beautiful golden yellow, with a dark patch across the back, and 

 the cœcal tubes of the intestine, likewise, very dark coloured, ovarial eggs 

 shining through the shell with a reddish orange hue. Colour of male 

 more uniformly yellowish. Length of adult female 1,60 mm., of male 

 1,32 mm. 



Remarks. This form is nearly allied to the well-known European 

 species, C. incongruois, Rambdohr., but easily distinguished by the much 

 more unequal size of the valves, pardy also by the form of the shell 

 and its colour. It also looks rather like the Australian species C. Sydncia, 

 which latter comes still nearer to the European form, and these 3 spe- 

 cies should, perhaps, be more properly referred to a (hstinct genus, hav- 

 ing some peculiarities of the shell in common, and also closely agreeing 

 in several other respects. 



Description of the female. 



Fully adult specimens attain a length of about 1,60 mm., and this 

 form, accordingly, grows to a somewhat larger size than both the Euro- 

 pean and Australian species named above. 



The shell is somewhat compressed (comp. figs. 4 a & 4 b), the great- 

 est width not nearly attaining the height. Seen laterally (fig. 4 a), it ex- 

 hibits a rather regular oval reniform shape, being about the same height 

 anteriorly as posteriorly, the greatest height but little exceeding half the 

 length. The dorsal margin forms a very slight, and quite even curve, 



