80 
AUG. F. FOERSTE 
of the band can be detected where the diameter of the shell is 
only 1.5 mm. On the last one or two volutions the median 
line frequently becomes obsolete, and the area of the slit-band is 
relatively flat. Not infrequently the slit-band is strongly 
convex across its entire width, the bordering striae are obsolete 
or have weathered away, and the general resemblance of the 
shell is similar to that of Lophospira producta Ulrich or Lopho- 
spira howdeni (Safford). In most of these cases the resemblance 
is striking only along the last 3 or 4 volutions, and the earlier 
volutions show the trilineate character of the slit-band with 
varying degrees of distinctness. 
The course of the transverse striae is the same as that indicated 
by Ulrich^i in his figures of Hormotoma. The lunulae traversing 
the slit-band transversely are well shown. The apertures, as 
far as preserved, are similar. 
Locality and Formation.' — Found in the large stone quarry 
half a mile northeast of Centerville Ohio, in the argillaceous 
strata immediately underlying the Brassfield limestone. 
Remarks.' — The relationship of this species appears to be 
with Hormotoma gracilis Hall and Hormotoma suhangulata Ulrich 
and Scofield, rather than with Hormotoma salteri Ulrich. At 
any rate, the surface of the volutions does not curve concavely 
upward on approaching the sutures above them. 
More than a thousand specimens were examined. This 
accounts for the numerous variations, some of which have been 
noted above. Some variations are represented only by a few 
specimens. For instance, in some cases the angulations above 
and below^ the slit-band are very distinct, and there may be 
even a second angulation present above this band. Individuals 
with an apical angle of 37° to 40°, and with only 8 or 9 volutions, 
also are relatively rare, but more than 20 specimens were noted. 
(Plate XV, fig. 4.) 
In one specimen with an apical angle of 35 degrees, 9.8 mm. 
wide at the base, 8 volutions are present, and 2 or 3 belong to the 
apical part, which is missing. The volutions in this case appear 
Idem., pi. 70. 
