the margin, which gradually slopes down to either extremity. 

 The ventral margin, as in the preceding species, is almost 

 straight, or with a rather indistinct sinus in front of the middle. 

 Seen from above (fig. 6) the shell exhibits an oblong oval form, 

 though comparatively a little broader than in C. dentato-margi- 

 natus. The anterior extremity is considerably narrower and 

 more pointed than the posterior, which is obtusely rounded. 

 The greatest width lies somewhat behind the middle and nearly 

 attains half the length. 



The valves are very unequal, the left being rather longer 

 than the right and overlapping it both anteriorly and posteri- 

 orly, as also along the ventral margin. On the other hand, 

 this valve does not by far attain the height of the right one, 

 which dorsally projects at a considerable distance beyond it, 

 forming the above mentioned gibbous prominence. The free edges 

 of the left valve are quite smooth and exhibit anteriorly and 

 posteriorly a rather broad pellucid border surpassed by fine 

 hairs. The right valve, on the other hand (see PI. Ill, fig. 12) 

 is distinguished by a quite similar regular crenulation of the 

 free edges as in the preceding species. The surface of the 

 shell is smooth and shining, without any perceptible sculpture, 

 and beset with fine hairs, more crowded at both extremities. 

 The impressions of the adductor muscle exhibit a quite similar 

 form and disposition as in the other species. 



The colour of the shell, in living specimens, rather agrees 

 with that in C. dentato-margiuatus, being light yellowish, clouded 

 with dark brownish shades. The latter form also in this species 

 2 irregular, partly confluent transverse patches, limiting a 

 lighter oval area just above the impressions of the adductor 

 muscle, the anterior of the patches being continued obliquely 

 downwards to the oral region. Moreover, as in the preceding 

 species, a narrow band of the same colour is found running at 

 a short distance from the anterior edges of the valves. Through 

 the shell the eye is more or less distinctly seen, as also the 

 coecal appendages of the intestine running diagonally from the 



