254 NEW YORK STATE MUSEUM 



the middle of the valve and from there to the hinge the valve is flat. 

 In the oldest portion of the shell, i. e. from the beak to about one 

 half the distance to the front, both valves present the appearance of 

 a typical C. acutiplicata (Con.) . But from this point to the 

 front the valves grow rapidly toward each other, thus producing a 

 very conspicuous thickening of the shell. With this thickening 

 there is an increased prominence of the concentric lamellae. The 

 dimensions of a large specimen are: length, 12mm; breadth, i6mm; 

 thickness, 9mm. 



This species which is from the very lowest Onondaga, immedi- 

 ately above the Esopus-Schoharie, evidently represents an offshoot 

 ofC. acutiplicata which, rapidly accentuating certain char- 

 acters, soon became extinct, for it was not found in any higher beds. 

 It must be regarded as a phylogerontic type, in which the characters 

 normal in the adult of its ancestors are lost in its own ephebic stage. 



Figured specimen, paleontologic collection, Columbia University, 

 catalogue no. 19,326. 



Leptocoelia flabellites (Conrad) 



One of the most characteristic Upper Oriskany species, and occurs 

 also less abundantly in the middle Oriskany. 



Whitfieldella? nucleolata (Hall) 



A^ery abundant in the Upper Manlius. The shell is small, an 



average one measuring 6mm by 5mm by 3mm in length, width and 



thickness respectively. It is not noticed in the Lower Manlius, while 



several specimens of the average size were found in the Favosites 



bed. 



Trematospira multistriata Hall 



Abundant in the Upper New Scotland ; it does not vary from the 



description of the type. 



T. perforata? Hall 



Several external molds and an internal mold of the pedicle valve 

 from the Upper New Scotland present the characters of this species. 



Nucleospira concentrica? Hall 



In the Lower New Scotland are many specimens of a shell which 



in external characters comes nearest this species but differs from it 



in the absence of a central, longitudinal, depressed line of the dorsal 



valve and in the fact that the dorsal valve is not depressed at the 



