198 
GEOLOGY OF THE FOURTH DISTRICT. 
This is a very abundant fossil, being found in the coarser shales over all the eastern part of 
the district. It resembles the figure of Modiola? semisulcata (Silurian Researches, pi. 8, 
fig. 6). 
Localities —Cayuga and Seneca lakes; Outlet of Crooked lake; Ontario and Livingston 
counties. 
79. 
1. Turbo lineatus, n. s. — Turbinate, obtuse ; surface marked by several sharp spiral lines, 
all which, except the central one, are not visible on the cast; longitudinally striated ; last whorl 
of the shell rapidly expanding; aperture orbicular ; umbilicus moderate. 
This fossil occurs generally as a cast, and in some places is abundant, frequently invested 
with a coral. 
Locality —Ovid, Seneca lake shore. 
2 and 3. Delthyris mucronata (Annual Reports of the New- York Geological Survey, 1841, 
p. 54). — Varying inform from semicircular to triangular, with the hinge line greatly ex¬ 
tended ; surface marked by 24 to 30 rounded ribs, which are crossed by crowded undulating 
elevated lamellae, giving a squamous appearance to the shell; hinge area very narrow; aper¬ 
ture small. Figure 2 is the nearly semicircular form ; fig. 3 shows the hinge line more ex¬ 
tended ; and fig. 3 of Illustration 84, presents a still more extended hinge line, from the shaly 
sandstone of the Third District. 
This is a very ornamental shell, and its numerous varieties in form are very interesting. 
In the soft calcareous shales of western New-York, it is shorter and more rotund; while in 
the sandy shales and shaly sandstones of the middle and eastern part of the State, it is greatly 
extended, and its extremities very acute. Occurs in all localities of the upper middle portion 
of the group. 
