32 2 NEW YORK STATE MUSEUM 



Dimensions. The largest shells of this species measure 4.5 mm in 

 length and about the same in hight (diameter of aperture). 



This well characterized species bears somewhat the same type of orna- 

 ment of B. 1 ed a Hall and other species of the Hamilton fauna which carry 

 expanded aperture and do not properly appertain to Bellerophon in its 

 restricted meaning. 



Habitat. Genesee province; Naples subprovince. In the Styliola 

 limestone, Bristol, Ontario co., and at Middlesex, Yates co. 



PHRAGMOSTOMA Hall. I 86 I 



The history of this name and the reason for employing it may be 

 briefly stated. In the Paleontology of New York, 1847, 1 : 183, James Hall 

 introduced the name Carinaropsis for a group of bellerophontids from the 

 Trenton limestone. In subsequently discussing this and allied genera, 1 he 

 states that the genus was founded on the external characters presented 

 by a few specimens. • " These are, the usually attenuated spire, the 

 abruptly expanding body volution, and shallow cavity, giving the shell a 

 patelloid aspect. To this may be added the character (perhaps not con- 

 stant) of an attenuated carina upon the dorsum." It is evident that the 

 internal characters of these shells were not known when the genus was 

 erected. Having subsequently received from the Lower Siluric beds of 

 Tennessee and Indiana, specimens bearing the external characters enumer- 

 ated and showing besides a kind of transverse plate or septum on the inner 

 lip, Hall suggested that, in case this latter character was not present in the 

 typical forms of Carinaropsis, these shells be designated by the term Phrag- 

 mostoma, and he proceeded to describe two species of these shells as C. 

 (Phragmostoma) cunulae and C. (P.) cymbula. The original 

 of Carinaropsis however did prove to bear this septum, and hence, so far as 

 this original employment of the term Phragmostoma is concerned, it was 

 synonymous with the former name. The next use of the term was its 

 employment by the same author 2 for the species we are about to discuss, 



X N. Y. State Cab. Nat. Hist. 14th An. Rep't. 1861. p. 93. 

 2 N. Y. State Cab. Nat. Hist. 15th An. Rep't. 1862. p. 60. 



