368 • PALEONTOLOGY OF NEW-YORK. 



Crtptonella, etc., I have found a shell of the form of the first named 

 genus, in which the dental lamellae of the ventr|j,l valve are united on 

 the back, forming a trough-shaped process, which is supported on a thin 

 septum extending for half the length of the valve. In the dorsal valve 

 there is likewise a simple median septum extending about one-third the 

 length of the shell, and which, on its upper margin, is expanded, forming 

 a shallow depression. No evidence of oral lamellae have been observed, 

 but in all essential particulars this internal structure is that of Camaro- 

 PHORIA ; and I shall thus refer the species, for the present at least. 



C'aiiiaroiilioria eucliaris (n. s.). 



PLATE LVII. 



Shell broadly ovate, length a little greater than the width. 



Ventral valve ovate, with the beak extended and arcuate, gibbous above 

 the middle, curving gently to the sides, broadly flattened or a little 

 depressed towards the front, and terminating upwards in a broad short 

 linguiform extension, giving the anterior margin an abruptly rounded 

 or truncate aspect. 



Dorsal valve gibbous in the upper part, more abruptly elevated along 

 the middle and towards the front, slightly concave on each side of the 

 broad undefined elevation : anterior margin sinuate. Beak closely 

 incurved into the cavity beneath the apex of the ventral valve. 



Surface marked by fine concentric striae, which at intervals are crowded 

 into lamelliform ridges. Shell apparently impunctate. 

 The interior of the ventral valve has a narrow liough-shaped process, extending 



about one-third the length of the shell, and supported on a thin median septum 



which extends bej-ond the anterior end of the troiigli. In the dorsal valve, the 



septum rises vertically for nearl}^ a third of the depth of the cavity einhiaccd hy 



the two valves, and has its upper margin abruptly and narrowly expanded. 

 The width, in two specimens, is three-fourths of an inch, and the length a little 



greater. 



Geological foiTnidion and localiti/. This fossil was collected in the Corniferous 



limestone of Canada West, by Mr. J. De Cew. 



