CEPHALOPODA— ORTHOCHOANITES. 5 5 



37. 0. cribrosum Geinitz. Carbonic. 

 Slightly more tapering than preceding, with septa close together, 



4 or 5 in the length of 5 mm. where the diameter is 5 mm. ; sur- 

 face with numerous, irregularly arranged, round pits (regarded 

 by some as foreign to the shell). 



Lower Coal Measures of Ohio and West Virginia; Upper Coal 

 Measures of Nebraska, Illinois, Missouri and Oklahoma. 



IX. Trematoceras Whitfield. 



Like Orthoceras but with a series of elongate tubercles on one 

 side, which appear to represent an interrupted series of elongate 

 openings in the body chamber, progressively closed by shelly de- 

 posits, as in Trematonotus or Haliotis. Devonic. 



38. T. ohioense Whitfield. (Fig. 1254, c,(/.) Devonic. 



Fig. 1256. Cycloceras lesueuri, FiG. 1257. Cyclocefas olorus, y^%. 



X %. (After Clarke, Pal. Minn.) (After Clarke, Pal. Minn.) 



Rather rapidly tapering; chambers short, about five equal to the 

 diameter of the upper one of them; siphuncle slightly excentric; 

 surface smooth except for nodes which are two to three times as 

 long as wide, and situated at every third septum in lower and 

 every second septum in upper part. 



Columbus limestone of Ohio. 



X. Protocycloceras Hyatt. 



Annulated Orthoceracones and Cyrtoceracones, with longitudinal 

 ridges or striations only in the early (nepionic) stages, in the 

 earliest of which the longitudinal sculpture alone exists. Siphuncle 

 large. Ordovicic. 



