386 PALEOZOIC PALEONTOLOGY. 
GASTROPODA. 
CYRTONELLA MITELLA Hall. 
Plate LIII., Fig. 12. 
1879. Cyrtolites (Cyrtonella) mitella Hall, Pal. N. Y., vol. V., pt. 
IT., p. 123, pl. 25, figs. 23-28. 
Description —‘Shell arcuate, subovoid, making altogether less than 
two volutions in the same plane; first volution very minute; the body- 
whorl rapidly expanding to the aperture, which is nearly circular; the 
peristome scarcely spreading; the shell carinate, and the casts obtusely, 
but distinctly, angular on the dorsum; apparently not sinuate or but 
slightly undulated on the anterior margin. Surface marked by regu- 
lar, sharply-elevated, subparallel, transverse strie, which are compara- 
tively distant (at least twice or thrice their width) near the apex and 
on the upper part of the outer volution, but become more crowded 
towards the front of the shell. On the upper part and sides of the 
shell the intermediate spaces are regularly cancellated by short, re- 
volving strie, which hardly rise so high as the transverse ones, giving 
the entire surface a pitted or finely-reticulate character. Approaching 
the margin the spaces between these strize diminish, as the result of 
the rate of growth in the shell, and they often become so crowded as 
to present the character of simple, undulating, granulose lines of 
growth. These striz are not sensibly curved in passing over the 
rounded carina. When the shell is partially exfoliated they give a 
lamellose-striate character to the surface.”—Hall. 
The dimensions of the best specimen observed in the New Jersey 
collection are: maximum diameter, 12 mm.; width of aperture, 11 
mm. 
Remarks.—This species occurs more or less commonly at the out- 
let of the Oak Ridge reservoir. The specimens are all internal casts, 
and the best-preserved ones closely resemble Hall’s illustrations of C. 
mitella, and it is believed that this identification is correct. . The sur- 
face markings described by Hall are, of course, absent from these 
internal casts, but upon some of them the transverse lines of growth 
may be detected, although they are never conspicuous. 
