1889. J 
291 
[Foerste. 
about 4.8 to 5 mm. The last half volution increases in size very 
rapidly, so as to give the entire shell a greatest diameter of 9 mm. 
This last half volution, in addition to being so’ ventricose, has an- 
other distinctive feature in being quite oblique towards the aperture y 
owing to an oblique flattening along the upper side of the volution. 
This, in some specimens, is very marked, in others it is not so no- 
ticeable. In some of the largest specimens, attaining a diameter of 
15 mm., this oblique flattening towards the aperture of the shell is- 
very marked. The spire, as a rule, is low, the older volutions rising 
but slightly above the level of the newer volutions in some speci- 
mens ; in others, the spire has quite an elevation considering the 
few volutions and their rapid increase in size. 
The largest elevation of any spire noticed was 2.5 mm. above’ 
the oral end of the last volution for a shell with a total height of 
8 mm., and a diameter of 8.7 mm. The least elevation of any spire 
noticed was 1.3 mm. above the oral end of the last volution in a 
shell 11 mm. high and 11.3 mm. in diameter. In the latter case, a 
view of the specimen with the aperture turned from the observer,, 
could not be distinguished from Fig. 3 a, pi. 28, Pal. N. Y. Vol. n,. 
representing Holopea obsoleta , Hall. As a rule, the spire of our 
specimens is more elevated. Holopea Guelphensis , Hall, from the 
Niagara of Wisconsin seems to us, judging from the figure published,, 
to belong rather under II. obsoleta as an extreme form of our variety 
elevata , than under the Canadian species described by Billings. In 
the Canadian species the increase in size of the volution is much 
less rapid, the same obliquity of surface is not noticed, and the 
vertical height of the shell is relatively greater. 
The same obliquity of the shell and rapid increase in size of 
the volutions, readily distinguish this from the small forms of 
Platyceras ( Platyostoma ) Niagarensis so characteristic of the Clin- 
ton strata of Ohio. 
Holopella? c/. Loxonema subulata, Conrad. 
(PLATE V, FIG. 21.) 
At Todd’s Fork, near Wilmington, Ohio, was found a single 
specimen with a long, conical spire, composed of seven or eight vo- 
lutions, increasing regularly in size ; the spire having a total height 
of 17 mm., the last volution having a diameter of about 7 mm. The 
volutions are evenly convex, and show no trace of a slit band in our 
specimen, nor of any surface ornamentations, except a few striae at 
