94 [Assembly 



DULA, extending from the posterior side one-third the distance 

 across the cavity. This septum is marked on the lower side 

 by a strong carina, and is concave above ; the margin a little 

 thickened as if from the folding over of the shelly laminae, and 

 posteriorly spreading over the volution behind in a callosity, like 

 many of the Bellerophon. This septum is a very peculiar fea- 

 ture, and, taken together with other characters, I conceive to be 

 of sufficient importance to warrant the separation from Bellero- 

 phon. Should this prove to be identical with those which I have 

 designated as Carinaropsis, that generic term will have prece- 

 dence ; but should this important character not be found in those 

 forms, I propose for those now under consideration the generic 

 name of Phragmostoma, from the septum within the aperture. 



CARINAROPSIS (PHRAGMOSTOMA) CYMBULA (n. s.). 



Volutions about two, enrolled in the same plane, very abruptly 

 expanding beyond the first volution, w^hich ie minute : width 

 of the aperture more than twice as great as the depth of the 

 cavity ; length of the septum about half as great as the width, 

 longitudinally carinate on the lower side and plane concave 



[ above, the posterior lip not reflected over the spire. The dor- 

 sum is marked with an elevated band, scarcely carinate, hav- 

 ing sometimes a faint groove in the centre and one on each 

 side. Striae of growth well defined, indicating a deep sinus at 

 the anterior margin. 



This species is sometimes distorted and the small spire broken or 

 eroded, whea it very much resembles a Crepidula. One specimen, when 

 entire, has had an aperture at least an inch and a half in diameter. 



Geological formation and locality. In strata associated with Cyrtolites 

 ornatus, and other fossils of the Hudson-river group, on the Ohio river 

 below Louisville. From Mr. S. S. Lyon. 



CARINAROPSIS (PHRAGMOSTOMA) CUNULJE (n.s.). 



Volutions two or more, the last one abruptly expanding, the 

 greatest expansion being two or three times as great as the 



