262 
AUG. F. FOERSTE 
same height are exposed in the vertical section exposing the 
siphuncle; this is followed by a shorter camera, and a trace of 
a second shorter camera. From this it is concluded that the 
conch was mature. The sutures of the septa are directly trans- 
verse to the axial diameter of the conch. At the base of the 
specimen the dorso-ventral curvature of the septum has a radius 
of 25 mm., and its radius of lateral curvature is scarcely 12 mm. 
The siphuncle is almost in contact with the adjacent wall of the 
conch. At the base of the living chamber the dorso-ventral 
diameter of the siphuncle is about 7 mm. , or about one-seventh 
of the dorso-ventral diameter of the conch. At the base of the 
specimen the dorso-ventral diameter of the siphuncle is slightly 
over 4 mm. The segments of the siphuncle intercepted between 
successive septa present slightly concave vertical sections along 
their walls. The lower margin of one segment invaginates into 
the upper part of the segment next beneath. The thickness 
of the siphonal wall is greater than that of the septa. There is 
no trace of an endocone. 
Locality and Horizon. — From the Orthoceras limestone on 
Victoria Head, at the northeastern angle of Bache Peninsula; 
regarded as of Canadian age. Collected by Per Shei in May, 
1899. Deposited in the Palaeontologisk Museum, Kristiania, 
Norway. 
Remarks. — This species almost certainly is congeneric with 
Clarkoceras newton-winchelli (Clarke), although it has not been 
possible to prove that the segments of the siphuncle are annular 
connecting rings, and not prolongations of the septal funnels as 
in the Endoceratidae. In Cyrtoc^rina the interior of the siphuncle 
has transverse ridges alternating with the septa between the 
camerae. I do not know the structure of Cyrtocerina well enough 
to determine whether this appearance of internal transverse 
ridges indicates a structure generically different from that of 
Clarkoceras. In such specimens of Cyrtocerina as I have seen 
only the casts of the interiors of the camerae have been retained, 
the substance of the siphuncle having disappeared. 
Clarkoceras newton-winchelli is from the Shakopee division of 
the Canadian in Union township in Houston county, Minnesota. 
