220 
AUG. F. FOERSTE 
19. ORTHOCERAS CLARKSVILLENSE SP. NOV. 
PLATE XLII 
Specimen 130 mm. in length, consisting of 16 camerae, of 
which the uppermost is distinctly shorter, suggesting that the 
conch had reached full maturity. The specimen apparently en- 
larges from a diameter of 21 mm. at its base to 28 mm. at its top, 
indicating an apical angle of about 4°. Near the. base of the 
specimen two and a half camerae occur in a length equal to the 
diameter of the conch. Toward the upper part, three camerae 
occur in a corresponding distance. The sutures are directly 
transverse. The septa have a concavity of 5 or 6 mm. at mid- 
length of the specimen. The center of the siphuncle is located 
about one-third of the diameter of the conch from its central side. 
The segments of the siphuncle are cylindrical in form and their 
diameter is about 3 mm. along the entire length of the specimen. 
No part of the exterior shell remains, but the cast of the interior 
of the conch is smooth and it is possible that the exterior of the 
shell was smooth also. 
Locality and Horizon. — Clarksville, Ohio ; either from the Lib- 
erty or the Waynesville member of the Richmond. 
Specimen No. 48255, in the U. S. National Museum. 
Similar specimens have been collected by Prof. W. H. Shideler 
in the basal part of the Liberty at Clarksville, Ohio; and in the 
lower Whitewiater, on Dodge creek, near Oxford, Ohio. 
A similar specimen, but with somewhat more distant septae, 
was found in the Richmond about a mile north of the light house 
at the southern end of Bay de Noc peninsula, in Northern Michi- 
gan, in strata probably equivalent to the Whitewater member.-^ 
Additional specimens have been found in the Stonington area, 
farther northward on the same peninsula, by Dr. R. C. Hussey, 
of the University of Michigan. 
Remarks. — It has not been determined to what extent the 
form of the segments of the siphuncle in Orthoceroids is depend- 
ent on the relative distance between the septa. In general it may 
be stated that in those forms in which the septa are more dis- 
tant from each other the segments of the siphuncle tend to ex- 
pand less within the camerae, sometimes being cylindrical, while 
Foerste, A., The Richmond faunas of Little Bay de Noquette in northern 
Michigan; Ottawa Nat., vol. 31, p. 122, pi. 5, fig. 19, 1917. 
