NIAGARA GROUP. 
289 
652. 2. ACROCULIA ANGULATA (». sp.). 
Px,. LX. Fig. 4 a-d. 
Apex attenuated, involute, forming one or two minute volutions, below which the shell ex¬ 
tends in a broad curve, expanding rapidly towards the aperture which is much dilated ; surface 
angulated, a sharp carina on the upper and lower outer margin of the volution, an obtuse carina 
on the middle of the back, and the inner margins angulated ; transverse section unequally 
pentangular; surface finely striated ; striae undulating over the surface, arching upwards on 
the sides, and downward or towards the aperture between the outer angles and the central 
carina, upon which they are twice undulated or bent. 
This species will be readily recognized by its angular form, which is always more or less 
perfectly defined. In many specimens the apex does not form visible convolutions, and in 
others there is sometimes a distinct volution of the larger part of the apex, so that the margin 
of the aperture is brought in contact with the upper part of the shell. There is likewise con¬ 
siderable variation in the degree of obliquity of the partial spire. 
Fig. 4 a. The back of a small specimen, where the shell is scarcely preserved. 
Fig. 4 b. Upper side of the same. 
Fig. 4 c. Back of another specimen, where the angles, carina, and surface striae are well preserved. 
Fig. 4 d. Upper side of the same, showing in part the expanded aperture and the minute volu¬ 
tions of the attenuated apex. 
Position and locality. In the shale at Lockport. A single specimen (very similar to this 
species, and perhaps only a variety of the same, forming a single volution nearly in the same 
plane) has been found in the upper limestone of the Clinton group at Lockport. 
[Paleontology — Vol. ii.] 
37 
