GASTROPODA. 917 
Bellerophon bilineatus.] 
next the lines of growth are more regular and sharper, then the slit-band is more 
truly a band though on the whole less prominent, while the lunulz are sharply 
defined. Finally, the inner lip is scarcely as broad though its inner margin is 
heavier, while the prominence of the central boss is emphasized by a deep and large 
depression on each side of it. We know of no other species with which B. clausus 
need be compared, excepting two or three of those next described. 
Formation and locality.—Trenton group, Frankfort, Kentucky, and near Nashville, Tennessee. 
Collection.—K. O. Ulrich. 
BELLEROPHON BILINEATUS, ”. sp. (Ulrich.) 
PLATE LXIV, FIGS. 19—21. 
Very much like B. troosti, only smaller, narrower across the aperture, with fine 
and sharper, as well as more regular, lines of growth, and much less prominent 
slit-band. The latter is concave, lies between two sharp lines and is crossed by 
rather distinct lunule. The posterior curve of the lines of growth on the dorsum 
also is broader, while the inner portion of the lower lip is much less thickened. The 
last difference is even more conspicuous when we compare the species with B. clausus, 
and this, coupled with the fact that the umbilicus is closed in that species and 
rather large in B. bilineatus, renders confusion with that form quite improbable. 
Formation and locality—Upper portion of the Trenton group, near Danville, Kentucky. 
Collection.—E. O. Ulrich. 
BELLEROPHON suBGLOBULUS, 2. sp. (Ulrich.) 
PLATE LXIV, FIGS. 17 and 18. 
This also resembles B. troosti very closely, but good testiferous examples may be 
distinguished without much trouble. The surface strie, though their direction 
with respect to the dorsal keel is nearly the same as in B. troosti (the retral curve 
on the back is somewhat wider), are more regular, sharper and thread-like. Com- 
paring other characters it is found that the volutions are more ventricose and more 
uniformly rounded, causing the shell as a whole to be more globular, the keel 
is less prominent and thinner, the aperture is more rounded and less 
expanded transversely, and the callosity of the inner lip not so great—probably 
much less. (In all of our specimens of this species the mouth is obscured by an 
incrustation of siliceous material so that we cannot tell exactly about the callosity 
of the inner lip.) B. subglobulus is distinguished from 6. clausus by similar 
differences, while the presence of a small umbilicus adds another, the umbilicus 
being closed in that species. In B. bilineatus the umbilicus is larger and the slit-band 
concave instead of rounded. 
