Cq)halopoda of the Cincinnati Group. 127 



The distance between the septa does not alv.ays increase uniformly, 

 sus the shell enlarges its diameter, but take a large number of chambers, 

 and the increased distance between the septa becomes manifest. It 

 is likely that the increased distance between the septa Ls more uniform 

 in rapidly tapering shells than in the longer and more slowly changing 

 oaes. 



Found on the hills back of Cincinnati ; range unknown. 



Specific name given in honor of Dr. R. M. Byrnes, of Cincinnati. 



Orthoceras Foderi—(S. A. Miller). 



Shell large and gradually tapering ; septa moderately arched, and 

 distant about one eigiith the diameter ; siphuncle excentric, enlarging 

 in an oval form in each chamber, and rapidly contracting at it? 

 passage through the septa, presenting the appearance of a string of 

 oval beads. 



A specimen, having a diameter of j%% inch at the small end, show- 

 27 septa in a length of 4.25 inches ; another specimen, having a diam- 

 eter of i%% inch at the small end, shows 15 septa in a length of 1.92 

 inches; and another specimen, having a diameter, at the small end, of 

 1 .50 inches, shows 20 septa in a length of 1.80 inches. 



This species most nearly resembles 0. Bynmi, but the distance 

 between the septa is less, and the siphuncle proportionally smaller, 

 while the specimens seem generally to be larger. 



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



(rroup. 



Specific name in honor of \\. B. Foster, Esq., who has a fine cabinet; 

 and kindly polished many specimens for my examination. 



Orthoceras Cincinnaiierms — (S. A. Miller). 



Shell medium size, rather rapidly tapering ; arch of the chambers 

 about half the distance between the septa, and septa distant about 

 two ninths the diameter of the shell ; siphuncle central, 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 a little more than the distance between the septa, while 

 tlie septa are pierced with holes, about one half the diameter of the 

 .siphuncle. 



The siphuncle of this species has a very close resemblance to that of 

 0. Bijrnesi, but the shell tapers more rapidly,, and the septa are more 

 dLitant and less arched. 



