CEPHALOPODA— AMMONOIDEA. 133 



192. P. ellipticum Hall and Whitfield. (Fig. 1384.) Siluric. 



Large, slightly curved ; section narrowly elliptical, very little 



wider on inner side ; ventral and dorsal height of living chamber 



Fig. 1384. Phragmoc. -'^, X H- (Pal. Ohio.) 



nearly the same; hyponomic sinus extended into a tube. 

 Guelph of Ohio. 



Order AMMONOIDEA. 



Climenida (Gastrocampyli). 



LXXII. AcANTHOCLYMENiA Hyatt. 



Costate whorls rather rapidly enlarging, moderately involute, 



suture with broad and high ventrolateral saddle and shallower 



lateral lobe; siphuncle dorsan, i. e., on interior of coil. Devonic. 



193. A. neapolitana (Clarke). Devonic. 

 Young with distant ribs, adult with fine, sharply forward arch- 

 ing striae. (Type of genus.) 



Naples shales (Portage) of New York. 



LXXHI. Platyclymenia Hyatt. 



Discoidal with costated whorls of subquadrangular section; 

 sutures with rounded lobes and saddles; siphuncle tubular, inter- 

 nal, with comparatively short funnels. Devonic. 



194. P. americana Raymond. (Fig. 1385.) Devonic. 

 Shell with numerous whorls, closely coiled but not involute; 



surface marked by rather distant ribs which do not cross the ven- 

 ter; suture simple; whorl section depressed; differs from the 

 associated P. polypleura Raymond in having fewer ribs, and from 



