GASTROPODA. 921 
Bellerophon capax.] 
expanded, extending below almost to the periphery of the outer volution; concave 
on each side of the latter, the inner edge thick and with a rounded central swelling 
which continues inwardly as a rounded ridge; inner aperture subtriangular, the 
inner or lateral angles rather sharp, the outer more obtuse. Surface marked by 
strong, regular, thread-like lines of growth, of which, on an average specimen, 
twelve to fourteen occur in5 mm. The course of the striz from the umbilicus to 
the slit-band is gently curved in the central half, but more strongly at each end. 
Slit-band very rarely preserved; when perfect it surmounts a low ridge, is of 
moderate width, concave, bordered on each side by a thin sharp line, and covered 
by more or less unequal lunulez. In casts of the interior the umbilicus is much 
larger, sharply defined and very abrupt, the ventral side of the volutions appearing 
to be almost flat and the section of the outer one triangular. 
This fine species is related to B. platystoma and B. similis, but has a thicker shell 
than either of the Trenton species. This shows itself especially in the much 
stronger development of the inner lip, and in the smaller umbilicus. As casts of the 
interior, in which condition all three of these species are most commonly met with, 
B. mohri may be distinguished from the others by the impression of the callosity of 
the inner lip which causes the umbilical cavity to appear as drawn out narrowly 
above. The volutions besides enlarge more rapidly, and the umbilicus, especially 
when compared with B. similis, is deeper and much more sharply defined. 
Good testiferous specimens are very rare, many being distorted by pressure, 
and in most of them the greater part of the aperture is broken away, and the 
surface markings obscured by weathering or maceration. The majority, however, 
preserve a large part of the expanded inner lip. 
Formation and locality.— Not uncommon in the upper part of the Richmond group of the Cincinnati 
period at Richmond, Indiana. We have it also from Lincoln county, Kentucky. 
Collection.—H.. O. Ulrich. 
BELLEROPHON OAPAX, n. sp. (Ulrich.) 
PLATE LXIII, FIGS. 50 and 51; PLATE LXIV, FIGS. 40—43. ° 
This species agrees closely with B. mohri, but on comparison proves to differ in 
a greater or lesser degree in nearly every feature. First, the volutions enlarge more 
rapidly, second, they are more ventricose, third, the umbilicus in casts is a trifle 
smaller and more rounded at the edge, fourth, the outline of the aperture is less 
narrowly rounded on the sides, and fifth, the cross-section of the outer volution of 
casts is nearer semicircular than triangular. The shell is larger, the volutions 
increase in size much faster, the umbilicus is smaller, and the inner lip much heavier 
than in B. platystoma and B. similis. When the aperture is imperfect, specimens of 
