132 



Cephalopoda of the Cincinnaii Group. 



The specimen being compressed a little at the large end, I can only 

 give the approximate diameter at 1.20 inches. There are fifteen septa 

 in the length of 2.30 inches, and their distance a^art increases as the 



Fig^. IG.—Cyrtoceras venlricosa. Longitudinal section, showing part of siphuncle. 



diameter of the shell increases. The distance between the first two 

 septa at the small end being 0.09 inch, and between the last two septa 

 at the large end, 0.24 inch. The fifth chamber from the small end 

 has a diameter of 0,62 inch; septa 0.13 inch apart; diameter of 

 siphuncle, within the chamber, 0.16 inch, and where it pierces the 

 septa about 0.03 inch. 



Surface apparently smooth, though the specimen is not in a condition 

 to definitely determine this point. Chamber of habitation and apex 

 unknown. 



I found this specimen and other fragments in the excavation for 

 Columbia avenue, east of Torrence road, in Cincinnati, at an elevation, 

 of about 150 feet above low water-mark. 



Cyrtoceras obscura — (S. A. Miller). 



Shell large, moderately curved, and very moderately enlarging 

 toward the aperture. Section subelliptical, transverse diameter 

 greatest. Septa slightly concave ; chambers thm, siphuncle beaded., 

 occasioned by the slight contraction in passing through the septa; 

 situated close to the dorsal side of the shell ; diameter about three 

 times as great as the distance between the septa. Shell slightly con- 

 tracted at the posterior end of the chamber of habitation. Chamber 

 of habitation and surface unknown. 



Specimen showing part of the chamber of habitation and fifteen 

 septa. Length of fifteen septa on the dorsal side, 3.40 inches ; ventral 



