42 G. o. sabs. [No. 8. 



Remarhs. — This species, though easily distinguishable from 

 the preceding, both as to the shell and the soft parts, undoubt- 

 edly belongs to the same genus. I think my identification of 

 the species will be found correct, though the figures and descrip- 

 tion given by Brady show a few apparent differences. 



Description. — The length of the shell in full-grown speci- 

 mens does not exceed 1,20 mm., and hence this species is consi- 

 derably smaller than the preceding. 



Seen laterally (PI. II, fig. 3) the shell exhibits a somewhat 

 reniform shape, though the contours appear a little more angu- 

 lated than in the preceding species. The greatest height lies 

 rather behind the middle, in the posterior part of the shell, and 

 does not quite attain the half length. The anterior extremity 

 is considerably lower than the posterior and obliquely rounded, 

 whereas the latter is broadly and obtusely truncate. The dorsal 

 margin is in the greater part of its length nearly straight and 

 somewhat ascending posteriorly, sloping with a rather abrupt, 

 nearly angulated, bend to either extremity. The ventral margin 

 is distinctly sinuated in the middle and joins the anterior and 

 posterior edges by an even curve. Seen from above (tig. 4) the 

 shell appears much compressed, exhibiting a very narrow oblong 

 form. The greatest width lies a little behind the middle and 

 does not much exceed y 3 of the length. The lateral contours 

 are evenly convex, and the anterior extremity much narrower 

 and more pointed than the posterior. The surface of the shell 

 in adult specimens is quite smooth, whereas in younger indivi- 

 duals a slight reticulation may be observed; it is sparingly^* 

 with tine hairs, as usual more distinct at either extremity. 



The valves are of rather firm consistency and some** 

 unequal, the left being in this form the larger and slightly over- 

 lapping the right at the extremities as also along the ventra 

 margin. The marginal part is highly chitinised and. as in 1 

 preceding species, in adult specimens distinctly grooved tnii) s - 

 versally (see PI. V, fig. 8). The inner duplicatures are very 

 large, especially their anterior part, which forms a broad, she • 

 like plate, bounded inwards by an obliquely curved line crossing 



