238 
AUG. F. FOERSTE 
rate of curvature as far as the most constricted part of the 
exterior wall of the siphuncle, and then appears to continue into 
the interior of the siphuncle for a distance of 1 mm., bending 
downward at an angle of 25° with a direct continuation of its 
course. On the ventral side of the siphuncle the septum curves 
gradually downward where in contact with the lower half or 
third of the overlying segment of the siphuncle, until reaching 
the most constricted part of the exterior wall of the siphuncle, 
beyond which it appears to extend into the interior of the 
siphuncle about half a millimeter in a direction toward the sim- 
ilar extension of the dorsal part of the septum. As a result the 
open passage through the center of the siphuncle appears to be 
constricted here to a narrow opening varying from 2 to 3 mm. 
in diameter. This constriction of the interior of the siphuncle, 
beyond the amount of constriction indicated by the exterior wall 
of this siphuncle, is not noted in all specimens, though traces of 
such constriction occur also in several of the segments in speci- 
mens obtained at Four Mile creek, near Oxford, Ohio. It is not 
regarded as a constant feature. Apparently it is not strictly a 
part of the septa, but was formed subsequent to the latter. 
In some specimens from 8 to 10 of the upper camerae are con- 
siderably shorter in length than the camerae beneath, indicating 
a rather long period of gerontic growth. 
The surface of the shell is transversely striated by lines which 
tend to occur at regular intervals, about 16 in a length of 20 mm. 
where the lateral diameter is 85 mm. Since similar distances 
obtain also toward the apical end, where the diameter is much 
less, the striae here appea-r relatively more distant. In some 
specimens the striae are more numerous, equalling 20 and even 
24 in a length of 20 mm. In general, these striae are of the 
^‘banded” form, or they may be very narrow and sharply defined, 
and separated by much broader flat areas. These transverse 
striae follow the same course as the former limits of the aper- 
ture. Along the median part of the dorsal side they are nearly 
directly transverse, but dorso-laterally they curve increasingly 
downward, their ventral course being broadly concave, forming 
broad and deep lobes here, whose bases lie about 5.5 camerae 
below the level of these striae on the dorsal side of the conch. 
These lobes mark former positions of the hyponomic sinus. 
Locality and Horizon . — This species was described from Rich- 
