GASTROPODA. 909 
OConradella dyeri.] 
transverse diameter relatively greater, the latter exceeding the vertical diameter by 
one-sixth, whereas the two dimensions are equal, or the hight the greater, in C. 
triangularis. Furthermore, the folds of the surface imbrications are fewer in 
number, there being only five or six on each of the dorsal! slopes to eight or nine in 
that species. Then the revolving ridges are more distinct, and the keel is more 
abrupt, especially on interior casts of C. grandis, the latter exhibiting distinctly 
a broad furrow on each side of the keel. The slit extends quite half around the 
last whorl. 
Formation and locality.—‘‘ Glade limestone” of the Stones River group, Lebanon, Tennessee, where 
the types (three specimens) were collected by Prof. J. M. Safford, and sent to one of the authors for 
description. 
CoNRADELLA DYERI Hall. 
PLATE LXVII, FIGS. 30—33. 
Cyrtolites dyeri HALL, 1871, Advance sheets, 24th Rept. Regents N. Y. St. Cab., and reissue of same, 
1872, p. 280, pl. vill, figs. 7, 8. M&EK, 1873, Pal. Ohio, vol. i, p. 149, pl. x10, 
figs. 2a, b, c, (not 2d and e, these representing C. elegans Miller), MILLER, 
1874, Cincinnati Quart. Jour. Sci., vol. i. p. 309. 
Shell small, 10 to 18 mm. in diameter, laterally compressed, consisting of two 
and a half or three volutions, the outer embracing the next within for about one- 
third of its hight. Whorls cordiform in section, broadest and sharply rounded 
below, sharply and abruptly carinate dorsally, rounded on the sides the curvature 
increasing downward from the keel; hight and width of volutions, including the 
carina, about equal, or the former slightly the greater. Umbilicus about equalling 
the dorso-ventral diameter of the last turn at the aperture. Surface marked by 
numerous closely and regularly arranged transverse lamelle, the raised edges of which 
are curved abruptly backward at regular intervals and have a general retral direction 
from the umbilicus to the keel. The recurved intervals being more prominent than 
the longer straight portions, and occurring at regular intervals, they cause the 
surface to appear as having revolving ribs. On the ventral half of the volutions the 
lower sides of the loops sometimes coalesce and form really continuous revolving 
lines. Ten of the loops on each side is the usual number for the last whorl, but two 
extra ones are sometimes distinguishable near the aperture of larger examples. Of 
the transverse lamelle the average number on the back of the last volution in 2 
mm. is seven or eight. The keel is prominent, rounded on the summit, and, so far 
as observed, without a trace of lunule, although some of the specimens before us 
are in a beautiful state of preservation, The slit has the usual length (i. e., nearly 
a half volution). 
