52 G- O. Sars. 



it is gradually narrowed to a somewhat twisted acute point, 

 whereas the posterior extremity is more obtusely rounded. 



The valves, at first sight, appear nearly equal. On 

 a closer examination, however, the left one is found to be 

 somewhat larger than the right, overlapping it anteriorly by 

 a narrow, hyaline border; and below the posterior extre- 

 mity a similar projecting rim may also be traced. As in 

 C. sydneia, the right valve exhibits at the anterior edge and 

 at the posterior part of the ventral one, a series of small 

 knobs or tubercles, giving the edge a minutely crenulated 

 appearance. The inner duplicatures are rather narrow, though 

 the anterior one is somewhat broader than the posterior. 



The surface of the shell is remarkably smooth and 

 polished, without any perceptible sculpturing, except the 

 usual small dots; and it is only at each extremity that it is 

 clothed with very small hairs. The muscular pits in the 

 centre of each valve are fairly conspicuous, and resemble 

 those in C. sydneia. 



The colour of the shell could not be ascertained, as 

 the specimens were discoloured by long immersion in spirit. 



The caudal rami (fig. 2 c) are of moderate size and 

 rather slender, tapering somewhat distally, and exhibiting a 

 slight flexure. They are armed in the usual manner, each 

 having at the end 2 unequal claws and 2 bristles The claws 

 are rather slender, the outer one being half the length of 

 the ramus. 



Occurrence. — A rather considerable number of this 

 pretty species were contained in a sample taken by Mr. Lea 

 from a pond «Near Hay». 



