CEPHALOPODA— CYRTOCHOANITES. 



117 



154. C. boycii (Whitfield). (Fig. 1352.) Ordovicic. 

 Rather stout, rapidly enlarging, and strongly convex, of de- 

 pressed, elliptical section, shallow camerae and highly nummuloidal, 

 siphnncle centren. 



Chazy of the Lake Champlain region. 



155. C. champlainense Ruedemann. Ordovicic. 



KiG. 1352. Cynadinoceras boycii^ with section and enlargement of part of siphuncle. 

 (After Ruedemann.) 



Rapidly enlarging, much less curved than preceding; siphuncle 

 smaller. 



Chazy of the Lake Champlain region. 



LXL GoNiocERAS Hall. 



Orthoceracones, extremely depressed dorsoventrally, with pro- 

 jecting lateral flanges, into which the septa are extended ; siphuncle 

 ventral, strongly nummuloidal ; septa with strong ventral and dor- 

 sal lobes. Ordovicic. 



156. G. anceps Hall. (Fig. 1353.) Ordovicic. 

 Large, rapidly expanding ; transverse diameters as i : 4 or 1:5; 



septa crowded, deeply lobed. 



Stones River of Minnesota and Tennessee; Black River of 

 New York and Canada. 



157. G. occidentale Hall. (Fig. 1354.) Ordovicic. 

 More rapidly expanding than the preceding; siphuncle large, 



