Description of Some Cincinnati Fossils. 



139 



Mr. Faber collected three specimens of this species, one of 

 which is illustrated, in the upper part of the Hudson River 

 Group, near Versailles, Indiana, and Prof. Hubbard and Mr. 

 J. F. Hammell collected a number of specimens in the same 

 range, associated with Crytocerina madisonensis, near Madi- 

 son, Indiana. 



Orthoceras ludlowense n. sp. 



Plate 7, Fig. 1, lateral view of ten chambers, also showing the 

 arching of the chambers ; Fig. 2, an end view, showing the 

 eccentric position of the siphuncle. 



This species is the largest known to the authors that has 

 been found in the Hudson River Group, about Cincinnati. 

 The shell is very large, robust, straight and gradually and 

 regularly enlarges from the apex to the mouth of the chamber 

 of habitation. The septa are distant and highly arched. A 

 transverse section of any of our specimens is subelliptical, 

 but it appears as if this might be due more or less to pressure. 

 Possibly a transverse section of a perfectly preserved speci- 

 men would be circular, though our specimens do not indicate 

 such to be the case ; we think all specimens will be found 

 somewhat flattened on the side near the siphuncle and proba- 

 bly on the side opposite thereto, as indicated by our specimens. 



The chamber of habitation, in one of our specimens, is 

 eight and one-half inches in length and is incomplete ; its 

 greater diameter, at the mouth, is four inches, and the greater 

 diameter, at the air chambers, two of which are attached, is 

 three and one-half inches. There are ten air chambers 

 illustrated, but the specimen is broken, and we have four more 

 air chambers that belong to the smaller end. The length of 

 the fourteen air chambers is ten and a half inches, the greater 

 diameter, at the larger end, is two and four-tenths inches, and 

 the greater diameter, at the smaller end, is one and forty-five 

 hundredths inches. These measurements indicate that the 

 total length of a specimen, four inches in diameter, at the 

 mouth, would be about three feet and a half. 



The smaller diameter of a specimen is a little more than 

 the length of two air chambers, and the greater diameter is a 



