248 
AUG. F. FOERSTE 
ing chamber is supposed to correspond to the much more pro- 
nounced gibbosity of Oncoceras constrictum Hall, but it is located 
farther up. 
The dorso-ventral diameter enlarges from 19 mm., at the 
base of the specimen, to 22 mm. at the base of the living chamber, 
the latter being 19 mm. farther up along the ventral side of the 
conch. At mid-height of the living chamber this dorso-ventral 
diameter is still 22 mm., but at the constricted part, 3 mm. be- 
low the aperture, it is only 20 mm., enlarging slightly above this 
point. Since the specimen is a cast of the interior of the shell, 
the apparent enlargement of the living chamber near its aperture 
may be due chiefly to a thickening of the interior of the shell 
there, - the exterior of the shell not showing any corresponding 
expansion. 
The conch is strongly compressed laterally, the lateral diam- 
eter at the base of the specimen being 15 mm. ; at the base of the 
living chamber it is 18 mm. ; about 2 mm. above this base it is 
18.5 mm. ; and from this point upward it diminishes gradually, 
until 3 mm. below the aperture, at the constricted part, it is 
15.5 mm. ; above this constricted part it increases slightly. The 
broadest part of the cross-section of the conch is distinctly dorsad 
of its center, the ventral side being much more narrowly rounded 
than the dorsal one, especially toward the aperture, whose con- 
tour is distinctly oval in outline. 
The sutures of the septa are directly transverse along the 
dorsal side of the phragmacone, and this direction is maintained 
along the dorso-lateral parts of the conch; but, on approaching 
the middle of the lateral sides, the sutures curve progressively 
more strongly upward, until they form an angle of about 75° with 
the ventral outline, when the cast of the interior of the phrag- 
macone is viewed from one of the lateral sides. The result is 
the formation of distinct saddles along the ventral side of the 
conch. The number of camerae, in a length equal to the dorso- 
ventral diameter of the conch at the top of the series of camerae 
being counted, is 8, when the counting is done along the ventral 
side. When compared with the corresponding lateral diameter, 
this number of camerae is slightly greater than 6. The septa 
are only moderately concave. The exterior of the cast of the 
interior of the phragmacone is marked by faint traces of vertical 
ribs, most readily detected on the dorsal side of the cast. 
