92 PALAEONTOLOGY OF NEW YORK. 
Surface marked by concentric, thread-like striae which, for a narrow space, 
are directed a little forward from the suture to a revolving crenulated 
carina, and thence make a gentle curve backward to the peripheral band, 
below which they are again directed forward with a scarcely perceptible 
curve; peripheral band tricarinate. The strige make a single retral curve 
across the space between the outer carinse, without essential interruption 
by the central line. 
The summit of the volutions is canaliculate just below the suture-line, and 
the striae bending forward from the suture are turned backward as they pass 
the carina limiting the narrow groove. The striae are distinct and thread-like 
in character, but not so coarse as in M. Leda, and the spire is less rapidly 
attenuate. The species is also distinguishable by the canaliculate suture 
and tricarinate 'band. # 
Formation and locality. In limestone of the age of the Upper Helderberg 
group, at Cambridge, Ohio. 
Murchisonia intercedens, n. sp. 
PLATE XXVIII, FIG. 29. 
Shell turreted; spire somewhat rapidly attenuate above. Volutions about 
nine in the length of a little over half an inch, angular and rapidly 
enlarging, the last one ventricose; the apex imperfect in the specimen 
described; the volutions about equally depressed-convex on each side of 
the peripheral band. Aperture broadly oval, a little longer than wide; 
columellar lip extended below and pointed. 
Surface marked by a narrow peripheral band in the middle and on the summit of 
the volutions, and the spaces above and below by rather strong transverse 
strise, which apparently cross the upper volutions almost vertically. 
This species has been seen only in the specimen figured, but its general 
form and the decided angularity of the volutions are sufficient to separate it 
from any other species of the formations under consideration. The specimen 
