184 PALEOZOIC PALEONTOLOGY. 
as much as 25°; the great majority of species measures exactly 24°. 
The New Jersey specimens usually lose their surface markings in 
being removed from their limestone matrix, and are usually broken 
up to such an extent that it is rare to secure fragments more than 
12 or 15 mm. in length. 
HELICOTOMA sp. 
In the faunas of the lower beds of the Jacksonburg section, and 
elsewhere, several specimens belonging to one or more species of the 
genus Helicotoma have been noticed. All of them are badly crushed 
and are in such a condition that they cannot be specifically identified. 
ECCYLIOMPHALUS TRENTONENSIS (Conrad). 
Plate XIIL., Figs. 20-21. 
1842. Cyrtolites trentonensis Conrad, Jour. Acad. Nat. Sci. Phil., 
vol. “Vie... p. 270, pl. a7, ne. 4. 
1847. Cyrtolites trentonensis Hall, Pal. N. Y., vol. L., p. 189, pl. 
40 A, figs. 3 a—d, pl. 41, figs. 1 a-c. 
Description.—Shell consisting of less than one volution, increasing 
gradually in size from the apex, coiled in one plane. Cross-section an- 
gularly subovate. Ventral side of the shell convex from the periphery 
to the inner margin; the periphery rather sharply rounded; about 
midway between it and the inner margin, on the dorsal side of the 
shell, is an angular, subcarinate ridge, the space between this ridge 
and the peripheral angulation being nearly flat; from the dorsal ridge 
to the inner margin of the shell the surface is convex. The surface 
is marked by rather obscure and irregular lines of growth, which, on 
the dorsal side, slope backward to the dorsal ridge, thus indicating 
the presence of an angular sinus in the aperture at that point. The 
most complete specimen observed has a length of about 35 mm. 
around the periphery of the shell from apex to aperture. 
Remarks.—This shell is apparently closely allied to H. subrotundus 
U. & 8. from Minnesota, and it is not altogether clear that the two 
species are really distinct. Cyrtolites trentonensis was not recognized 
