Review of the New York Geological Reports. 63 
The whole of the above seem to be American species except- 
ing fig. 5, which is believed to be identical with a species figured 
by Phillips. Fig. 9, Modiola concentrica is thought to resemble 
in some respects Modiola (?) semi-sulcata which occurs in the 
lower Ludlow rocks of the Silurian system. (See Silurian Re- 
searches, pl. 8, fig. 6.) 
4 
Hall’s Report. (79.) 
2 
zy 
— 
Fig. 1. Turbo lineatus. 2 and 3. Delthyris mucronata. 4. Atrypa prisca. 
A few of these fossils are identical with western species. The 
Atrypa prisca, as already remarked, is abundant in the water lime- 
stone and shale beds below the black slate, but we have not ob- 
served it either én or above that formation. At the Button-mould 
gradations from one extreme to the other, that they have been 
