OB' DENISON UNIVERSITY. 
37 
The surface is marked by rather obvious concentric lines. The pos- 
tero-inferior projection is greater than that of the hinge line. Fig. 13 
of Plate IV, represents a specimen in which part of the posterior out- 
line is obscure, while that figured on Plate III, Fig. 12, had its ante- 
ro-inferior outline crushed in. By combining the figures a fair idea 
of the shell can be obtained. The specimen figured on Plate IV, 
is much flattened and somewhat distorted, it should be restored by 
producing the upper, posterior angle and the lower, posterior lobe. 
From A. longa, which it most resembles, it differs in being not only 
larger, but less produced posteriorly, the posterior sinus is much less 
and the anterior part of the shell does not appear to have the oblique 
sulcus described for that species. (We have, since writing the above, 
found the long posterior tooth characteristic of Avicula.) 
Myalina {cf. recurvirostris, M. and W.) 
N (Plate V, Fig. 4.) 
A single fragment indicates a species of nearly the size of the spe- 
cies quoted. It is not sufficient, however, to furnish the basis for ac- 
curate identification. The outline probably is not correctly restored 
in our drawing, but the shell was flattened, causing uncertainty as to 
the natural course of the striae. The surface is marked by very coarse 
but regular and distant furrows, as well as the finer concentric lines. 
Myalina sp? 
(Plate IV, Fig. 20.) 
Only a small fragment was found to indicate a species, like M.. 
Meliniformis, M. and W. It belongs to the group of M. subquadrata, 
M. sublamellosa, Eldridge, M. perattenuata. Meek, M. Flemingii, 
King, etc., but is a very small species, with acute beaks and strong 
striae. 
Myalina {?) SWallovi, McChesney. 
(Plate IV, Fig. 6 ) 
This familiar and widely distributed species is common here also. 
The general aspect is unlike most species of Myalina, but more like 
