330 PROCEEDINGS OF THE ACADEMY OF 



and one of the assistant geologists of the Ohio Survey, who dis- 

 covered the specimens from which the foregoing description was 

 made out. 



Locality and position. — Base of Coal-measures, near Somerset, 

 Perry County, Ohio. 



CEPHALOPODA. 



ORTHOCEEAS ORTONI, Meek. 



Shell rather rapidly expanding from the posterior toward the 

 aperture ; section oval or more or less nearly circular ; septa 

 rather closely arranged ; siphuncle lateral, being at one of the 

 narrow ends of the compressed section, but not quite marginal, 

 of comparatively moderate size, and apparently beaded ; surface 

 of cast showing traces of regular, obscure, longitudinal ridges, 

 that would probably not have been defined on the exterior of the 

 shell, which is unknown. 



I have seen but two specimens of this species, and they are 

 accidentally compressed, and incomplete at both extremities. The 

 more nearly complete one of these specimens is about 2.30 inches 

 in length, and septate throughout. At the larger end, it measures 

 about 1.3T inches in breadth, and only 0.44 inch in its smallest 

 diameter; while, at the smaller end, its greater diameter is 0.38 

 inch, and its smaller 0.24 inch. It has manifestly, however, been 

 accidentally compressed, more strongly at the larger end, which 

 gives the appearance of more rapid expansion toward the aper- 

 ture than the natural form. The septa near the larger end are 

 separated by spaces measuring 0.15 inch, and at the smaller end 

 measuring 0.0*7 inch. At the larger end, the very obscure longi- 

 tudinal ridges measure each about 0.05 inch in breadth, with fur- 

 rows of the same breadth between, and both diminish propor- 

 tionally in size, and become nearly obsolete toward the smaller end. 



Tills species evidently belongs to the section of the genus con- 

 sisting of rather rapidly expanding shells, with a nearly marginal 

 siphuncle, sometimes showing faint longitudinal ridges on the in- 

 ternal cast, that are not defined on the external surface ; such, for 

 instance, as 0. comjnilsiim, O. robustum, 0. indocile, &c. &c., of 

 Bai'rande. It resembles several of Dr. Barrande's Bohemian 

 species of this type ; but, after repeated comparisons, I have been 

 unable to identify it with any of the numerous species described 



[March 19, 



