38 G. o. SARS. M.-N. Kl. 



hand, much elongated, with the terminal part doubled upon the proximal 

 one. Spermatic ducts in male forming within the anterior part of each 

 valve a dense coil; mucou.s glands comparativeh' small and narrow. 



Remarks. This new genus is chieOy characterised bv the unusual 

 development of the caudal rami, \\'liich form exceedingly powerful loco- 

 motive organs. Moreover, in the structure of the cœcal appendages of the 

 intestine, the ovarial tubes and the spermatic ducts, it differs rather con- 

 spicuously from the other genera. It is, as yet, only represented bv a 

 single species. 



15. Cypricercus cuneatiis, G. O. Sars, n. sp. 

 (PI. 6, fig. fig. I, a— h.) 



Specific Characters. Shell in both sexes rather tumid, the width 

 even exceeding the height: — seen laterally, oblong cuneiform, highest in 

 front, dorsal margin slightly arched, \'entral somewhat convex, with an 

 indistinct sinus in front of the middle, anterior extremity broadly rounded, 

 and Hanked by a hyaline border, posterior obtusely acuminate: — seen 

 from above, oblong oval, greatest width behind the middle and nearly 

 eciualling half the length, both extremities obtuse. Valves somewhat un- 

 ec^ual, the left o\^erlapping the right both anteriorly and A'entralh', A\'hereas 

 it is slightly overlapped by the right at the posterior extremity; inner 

 duplicatures not very Inroad. Caudal rami, including the claws, exceeding 

 half the length of the shell, sublinear, hneh- denticulated inferiorly, distal 

 claw about ^/g as long as the ramus. Colour of female, yellowish, clouded, 

 dorsally with light green ; that of male, generally more uniformly ochra- 

 ceous. Length of adult female 1,75 mm., of male 1,55 mm. 



Remarks. This is, as abo^x- stated, the only as yet kno\\'n species 

 of the genus, and may at once be recognized by die peculiar shape of 

 the shell, and by the greatly developed caudal rami. 



Description of the female. 



The length of fully adult specimens measures 1,75 mm., whereas 

 the greatest height is only 0,80 mm. 



The shell is rather narrow, but comparatively tumid (comp. figs, i a & 

 1 b), the greatest width even exceeding the height, and has the dorsal face 

 somewhat fiattened posteriorly. Seen laterally (fig. 1 a\ it cxhil)its a rather 

 peculiar form recalling somewhat that in the marine Cytherid BytliocytJicre 

 simplex Norman, being oblong cuneiform in outline, with the greatest 

 height not attaining half the length, and occurring in front of the middle. 

 The dorsal margin is slightly, and somewhat irregularly curved, with its 



