138 
PALAEONTOLOGY OF NEW YORK. 
of the fossil is that of a flattened Pleurotomaria,— the upper side of the volu¬ 
tions being depressed towards the spire. 
These characters of mouth and peripheral band are scarcely compatible with 
those of the genus Euompiialus, as understood from descriptions, or as usually 
represented in the figures of the typical form of the genus. The Euompiialus 
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 Pleurotomariidm ; 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 Euompiialus with the specimen under consideration; 
and therefore I must leave undecided for the present, its positive relations to 
that group of fossils. 
