128 Cephalopoda of ilic Cincinnati Group. 



Fouiul on the hills back of Cincinnati ; range unknown. 



A very handsome specimen of this species, in the cabinet of C, B. 

 Dyer, Esq , about six inches in length, diameter at the small end y^(jthf; 

 inch, at the large end 1.15 inches, contains forty two chambers. 



Orthocpras Halli — (S. A. Miller). 



Fig. 14. — Orlhoceras Halli. Longitudinal section, showing siphuncle. 



Shell large, rapidly tapering; septa distant about one sixth the 

 diameter of the shell ; siphuncle excentric, or crossing from one side to 

 the other, and consisting of a series of slightly ovate enlargements in 

 each chamber. The greatest diameter of the siphuncle is about one 

 and a quarter times the distance between the septa, while its diameter, 

 where it pierces the septa, is about one half the distance between th'e 

 septa. Body chamber about one third the length of the shell. Surfaere 

 unknown. 



Found in the upper part of the Cincinnati Group, in Clinton county, 

 Ohio. 



The specific name is given in honor of Prof. J. W. Hall, of Coving- 

 ton, Ky., who kindly furnished me his specimens for study. He has 

 one specimen showing the body chamber four inches in length, 

 diameter at the mouth, slightly compressed, two and a half inches, at 

 the rear end two inches (true diameter at the mouth probably not 

 much exceeding two inches). Seventeen chambers, next to the body 

 chamber, are four inches in length ; the shell at the seventeenth 

 chamber being a little over one inch in diameter. 



Orfhoceras Harperi — (S. A. Miller). 



Shell medium size, rather rapidly tapering; septa moderately arched, 

 and distant about one ninth the diameter of the shell; siphuncle 

 excentric, or crossing from one side to the other, and consisting of a 

 series of longitudinally depressed ovate enlargements in the chambers. 



