CEPHALOPODA. 109 



No. 249. Orthoceras Duseri. H. & W. 



la this type genus the shell is straight; siplmncle complex and nearly cen- 

 tral, and the aperture sometimes contracted. From the Cincinnati Group, 

 Waynesville, Ohio. 



No. 250. [585, Cast]. Orthoceras amplicameratum, Hall. 



On slab. This handsome specimen from the Trenton Limestone (Lower 

 Silurian) of Middleville, N. Y., shows the entire length of the last chambers, 

 with faint traces of the mouth. The shell being gone, the chambers of the 

 posterior portion are visible. The original is now in the Ward Collection, 

 University of Rochester. _ Size, 9x4. 



No. 251. Eudoceras proteiforme, Hall. 



This genus has the shell elongated and cylindrical, and the siplmncle large, 

 eccentric, and containing conical tubes or diaphragms. From Utica Shale 

 (Lower Silurian), Holland Patent, N. Y. 



No. 252. [592, Cast]. Gomphoceras inflatum, Quenst. 



This genus is characterized by a form spindle-shaped or sub-spherical, pro- 

 duced by an abrupt tapering or contraction of the last chamber towards the 

 mouth; which latter is frequently of a very sinuate and irregular form. This 

 specimen, which shows the septa and the last chamber, is from the Middle 

 Devonian of the Eifel, Rhine Valley, and is now in the Ward Collection of 

 the University of Rochester. 



No. 253. [598, Cast]. Cyrtoceras macrostomum. Hall. 



The Cyrtoceras differs from Orthoceras chiefly 

 in the eccentric siplmncle, and in the direction of 

 its shell, which is simply arched or bowed like a 

 horn, but never rolls up in a spiral. Barrande 

 has described nearly two hundred and fifty species 

 from the Silurian of Bohemia. This specimen is 

 from the Trenton Limestone (Lower Silurian), Mineral Point, Wisconsin. 



No. 254. [602, Cast]. G-yroceras trivolvis, Hall. 



This shell is nautiloid; whorls separate, and the 

 siphuncle eccentric and radiated. The genus is ver}' 

 closely related to Lituites. From the Upper Helder- 

 berg (Devonian) of Schoharie Co. , N. Y. 



Diameter, 6. 



