363 
PALAEONTOLOGY OF NEW-YORK. 
Cryptonella, etc., I have found a shell of the form of the first named 
genus, in which the dental lamellae of the ventral 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. 
Camapojtlioria euciiaris (n. s.). 
PLATE LVII. 
. Shell broadly ovate, length a little greater than the width. 
V:entral 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^oncave 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 trough-shaped process, extending 
about one-third the length of the shell, and supported on a thin median septum 
which extends beyond the anterior end of the trough. In the dorsal valve, the 
septum rises vertically for nearly a third of the depth of the cavity embraced by 
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 formation and locality. This fossil was collected in the Corniferous 
limestone, of Canada West, by Mr. J. De Cew. 
