30 G- O. Sars. 



short, but rather wide, and somewhat blunted at the tip. Tlie 

 posterior extremity is less broad and more produced, being 

 narrowly rounded at the tip, and defined from the dorsal edge 

 by a distinct angle. 



Seen from above (fig. 2), the shell exhibits an oblong 

 oval form, wâth the greatest width uot quite half the length, 

 and occurring in its anterior part across the umbones. The 

 anterior extremity appears more obtuse than the posterior 

 which is narrowly pointed. 



The valves, which admit of being perfectly closed all 

 round, exhibit outside numerous very conspicuous and some- 

 what elevated lines of growth, amounting to about 24 in all. 

 These lines are, in the central part of the valves, rather regular, 

 and placed at nearly equal intervals, but become more densely 

 crowded towards the periphery. When viewed Avith a high 

 magnifying power, the outer lamella of the shell appears very 

 finely striated between the lines of growth, in a radiating 

 manner (see fig. 4); but the edges of the valves are quite 

 smooth, without any trace of spines or bristles. 



The animal (see fig. ö) is comparatively rrore voluminous 

 in proportion to the shell than in the genus Euli)nadia (and 

 Limnadia), but is yet enabled, by a strong curvature of its 

 anterior and posterior parts, to withdraw itself completely 

 within the cavity of the shell. It is composed of the same 

 principal parts as in Eulimadia, and is attached to the shell 

 in quite a similar manner. 



The division of the body extending in front of the dorsal 

 ligament, is generally strongly deflexed, but admits of being 

 somewhat raised so as to throw its outer part more or less 

 beyond the anterior edges of the valves. As in Eulimadia-, 

 this division is composed of 2 well-marked parts, the cervical 

 segment and the head, both defined dorsally by a deep in- 

 cision. The head is rather large and of an appearance very 

 different from that in Eulimadia (and Limnadia). 



