OF THE FAMILY OF NAIADES. 451 



the very point of the beaks, in the right valve lamellar near 

 the termination, and abrupt ; in the left acicular, the channel 

 being only large enough to admit of the edge of a penknife ; 

 in the right valve the cardinal and lateral teeth are entirely 

 separated by a cavity formed by the tooth of the other valve, 

 this cavity is at the very point of the beak, and therefore the 

 valve has little or no cavity ; in the left valve the large recurv- 

 ed tooth forms a beautiful angular cavity ; anterior cicatrices 

 distinct ; posterior cicatrices confluent ; dorsal cicatrices situ- 

 ated at the point of the cavity of the beaks ; cavity of the shell 

 very shallow ; nacre delicate salmon colour towards the beaks, 

 bluish towards the margin. 



Remarhs. — This is a singular and beautiful shell. Its 

 cardinal and lateral teeth are very remarkable. The first 

 being high in the left valve over the cavity of the beak, while 

 in the right it is there depressed ; the latter is short and 1am- 

 elliform at termination. The beaks are equally remarkable, 

 being finely undulated ; the epidermis is so thin and delicate 

 as to give them almost a white appearance. The rays are 

 broader and more full than in any shell I have seen ; they 

 diverge in all directions from the point of the beaks to the 

 margin. 



The specimen belonging to the cabinet of the New York 

 Lyceum, was kindly sent for my inspection by W. Cooper, 

 a member of that valuable institution. It was given by Dr 

 Eights to Mr Barnes, and by the latter labelled "K alasmo- 

 dontlna." My description was written some years since, but 

 remained unpublished until I should have an opportunity of 

 examining other specimens. 



VOL. III. — 5 Y 



