295 
[Foerste. 
2. This form was described by Hall, in 1843, as Strophomena 
elegantula , although the accompanying figure of that date suggests 
rather the Leptcena sericea of Lower Silurian strata. The figures 
published in 1851, show affinities with Leptcena transversalis as the 
earlier description suggests. 
2. In the collections from the Clinton of Indiana, a similar form 
is quite common. The largest specimen is 10 mm. long and 17 
mm. broad. The interior of the shell is punctate, the punctse be- 
ing connected with the exterior striae, therefore occurring in rows. 
Occasionally a very irregular and indistinct set of lines pass be- 
tween these punctce, but this seems an accidental feature and not 
at all comparable with the figure published by Hall under Leptcena 
transversalis. The ventral valve is strongly convex, the dorsal 
moderately concave. 
The stronger radiating striae are very prominent and the inter- 
mediate regions are often faintly concave. The beak is slightly 
broader than in the New York Clinton specimens. These Clinton 
specimens of New York and Indiana are placed under Leptcena 
transversalis , as variety elegantula , adopting Hall’s earlier specific 
name It includes those forms with a moderately distinct beak, a 
shell of medium convexity and prominent, strongly- elevated inter- 
calated striae. The interior I have not seen. 
Leptcena quinquecostata , McCoy, has most of these features. 
2. A small Leptcena i, of which an average specimen is 11 mm. 
broad and 6 mm. long, is found at Collinsville, Ala. The dorsal 
valve is of about the same convexity as the variety elegantula from 
New York, but the cardinal extremities are more prolonged, some- 
what after the fashion of the variety prolongata. The surface is 
marked by fine radiating striae with stronger, more prominent, sin- 
gle striae interspersed, in one individual leaving the intermediate 
area slightly concave by way of contrast with their own elevation. 
This form we consider a depauperate representative of the variety 
elegantula in the same way that the variety Alabamensis hereafter 
to be described is considered a depauperate representative of the 
more typical forms of Leptcena transversalis. It has also features 
similar to Leptcena quinque-costata , McCoy, especially in the strong 
elevation of the prominent intercalated strife. 
3. Leptcena transversalis , Hall, of the Niagara strata of New 
York, has a more strongly convex ventral valve, the beak being 
strongly incurved, extending beyond the cardinal margin and ap- 
