774 THE PALEONTOLOGY OF MINNESOTA. 



LOyrtoceriiui schuoluruf U . 



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 Chatfleld, Minnesota. Collec- 

 tions of W. H. Scofleld and E. O. Ulrich. 



Museum Register, No. 7631. 



Nan.no belemnitiforme Holm, is from the upper red OrMioceras-liniestone on the island of Oeland, 

 from the lowest beds of the .Ec7tnospJiem<-limestone in Esthland, and from boulders of like age at 

 Heegermtihle 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 Endoceratidce 

 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 5 mm. 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 



dcr\t&%_ 



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. la the Trenton shales, one-half mile southeast of Cannon Falls, Minn. 

 Collection of E. O. Ulrich. 



