293 
[Foerste. 
below slightly exceeding the flattening of the upper side of the vo- 
lution. 
I have never seen Euomphalus sinualus , Hall, from the Lower 
Helderbergof New York, but the striae as figured would agree pre- 
cisely with those of our specimens if the upper side of that speci- 
men were called the lower, and the reverse. 
The Lower Heidelberg form, is however, figured as a sinistral 
shell, while mine is undoubtedly dextral, but this very fact might 
account for the reversed character of the striae. No sinus similar 
to that in the Alabama specimens seems to have been noticed. My 
specimens are too fragmentary to warrant a new specific name. 
Lept^ena transversalis, Dalman. 
A, var. elegantula ; B , var. Alabamensis ; (7, var. prolongata. 
(A, PLATE VI, FIG. 6 ; B , PLATE V, FIG. 9 ; (7, PLATE V, FIG. 13.) 
Leptcena sericea , from the Trenton Group of New York, agrees 
quite well in size and degree of curvature with the more convex Eu- 
ropean types, with very fine radiating striae with which are inter- 
calated at intervals of six to eight striae, single inconspicuous striae 
of greater width and elevation. Slightly less curved shells with 
about ten equally fine striae, in a width of 1 min., occur in the same 
group. With the flattening of the shell, however, as a rule an in- 
crease of the size of the striae seems often to be correlated. Thus 
at Cincinnati, Ohio ; along the Ohio, opposite Maysville, Kentucky ; 
near Huntingdon, Pa.,— all of the Hudson River Group, the curva- 
ture of the shell is only of a medium degree, the more prominent 
striae occur at intervals of four to six of the finer striae, and eight to 
eight and one-half striae occur in a width of 1 mm. 
Between Millheim and Centrehall, Pa., and at Pointe Claire, oc- 
cur specimens with but moderate convexity, usually quite decidedly 
flattened for this species, with six and one-half to seven striae in a 
width of 1 mm., the intercalated coarser striae recurring at intervals 
of four to six, oftener four striae. At Rowland’s Mills’ Quarries 
near Saratoga, New York, a quite flat form occurs with about the 
same number of striae. In a specimen from Tennessee, also with 
but moderate convexity, there are six striae in a width of 1 mm., 
and the stronger striae recur at more irregular intervals, of from 
two to four striae. Correlated with the increase of the size of the ra- 
diating striae seems to be the development of concentric striae which 
