138 PALAEONTOLOGY OF NEW YORK. 



of the fossil is that of a flattened Pleuuotomaria, — the upper side of the volu- 

 tions heing depressed towards the spire. 



These characters of mouth and peripheral band are scarcely compatible with 

 those of the genus Euomphalus, as understood from descriptions, or as usually 

 represented in the figures of the typical form of the genus. The Euomphalus 

 Wahlenbergii of Goldfuss possesses the peripheral band and all the essential 

 characters of our species, and is clearly congeneric with it. 



Chenu, in his description of the genus, recognizes a more or less deep sinu- 

 osity in the external lip, and the presence of a peripheral band ; and Prof. 

 McCoy suggests the necessity of subdividing the genus, and separating those 

 " with rounded whorls and a circular, entire mouth," from those with angular 

 volutions and " a slit in the outer lip, as in Schizostoma." 



If the features described and illustrated in the species under consideration 

 are characteristic of the typical form of the genus Euomphalus, then it seems 

 proper that it should be referred to the family Pleurotomariidaj ; otherwise, 

 this fossil should be designated as a new generic form, for which I would 

 propose the name Pleuronotus, with the following diagnosis : 



PLEURONOTUS, n. gen. 



Shell discoid. Volutions slightly oblique to. the plane of the shell, gradually 

 enlarging from a minute apex ; concave above and below. Umbilical side 

 broad, and the depression shallow ; spire concave ; external lip with a 

 distinct sinus. Surface, on the summit, and partially on the external side 

 of the volution, marked by a distinct band, to the margins of which the 

 surface-striae converge on the two sides, and upon which they make a 

 regular retral curve. 

 The relations of this fossil (E. Decewi) with Pleurotomaria are quite obvious ; 



but unfortunately I have not at this time the means of comparing authentic 



Carboniferous forms of Euomphalus with the specimen under consideration; 



and therefore I must leave undecided for the present, its positive relations to 



that group of fossils. 



