774 THE PALEONTOLOGY OF MINNESOTA. 
{Cyrtocerina schoolcrafti. 
substance strongly suggest that genus, even though there is little superficial 
similarity in the relations of these parts to the septate portions of the shell in the 
two genera. 
Formation and locality.—The material which has been studied consists of seven specimens obtained 
from the Trenton shales at Minneapolis and from the Galena shales near Chatfield, Minnesota. Collec- 
tions of W. H. Scofield and E. O. Ulrich. 
Museum Register, No. 7631. 
Nanno belemnitiforme Holm, is from the upper red Orthoceras-limestone on the island of Oeland, 
from the lowest beds of the Hchinospherites-limestone in Esthland, and from boulders of like age at 
Heegermiihle in the vicinity of Eberswalde. 
Genus CYRTOCERINA, Billings, 1865. 
The shells which have been referred to this genus are cyrtoceran in form and 
are characterized by the great size of the sipho, which is situated on the ventral side 
and is not fully enclosed by the septa. Hyatt places the genus with the Endoceratide 
and considers it of similar structure to Piloceras, with inverted siphonal sheaths, 
though no conclusive evidence of such structure is to be derived from Billings’ descrip- 
tions of the two known species, C. typica, from the Black River limestone, and C. 
mercurius, from the Quebec group. The species herewith described is provisionally 
referred to the genus on account of the ventral position of the sipho and general 
agreement in the form of the shell. It is the only specimen among the cyrtoceran 
shells in the Silurian material from Minnesota which possesses this feature, and 
though many Silurian and Devonian species having the septa thus placed have been - 
referred by authors to Cyrtoceras, I hesitate to place this shell in that association. 
CYRTOCERINA (?) SCHOOLCRAFTI, sp. nov. 
PLATE XLVII, FIGS, 12—14. 
This form is represented by a small portion of a very rapidly expanding and 
sharply arcuate shell, which, in a length of 7 mm., tapers from a dorso-ventral 
diameter of 10 mm. to one of 5mm. The outlines of the septa are distinctly ovate, 
broadest toward the ventral side and subacute on the dorsum, the dorso-lateral 
surfaces being somewhat compressed and the obscurely ridged dorsum a noticeable 
feature of the exterior. Sipho ventral, submarginal and fully enclosed, large in 
comparison with species of Cyrtoceras. On the lagert septums, which has a diameter 
of 10 mm. the sipho is 14 mm. in diameter. Septa apparently closely appressed. 
External shell surface marked by faint concentric growth-lines. 
Formation and locality—In the Trenton shales, one-half mile southeast of Cannon Falls, Minn. 
Collection of E. O. Ulrich. 
