CEPHALOPODA— AMMONOIDEA. 



165 



fine; differs from P. knoxvillense in the more rapid widening 

 towards the aperture, and in the coarse folds on umbiHcal half 

 of the whorl. 



Portlandian of the Mazapil district, Mexico, also Europe. 



269. P. mazapilense Burckhardt. (Fig. 141 1.) Jurassic. 



Smaller than preceding; compressed whorls gradually widening 

 with growth ; costse faint or obsolete ; suture finely divided, sad- 

 dles bifid. 



Portlandian of the Mazapil region of Mexico, not rare. 



270. P. knoxvillense Stanton. (Fig. 141 2.) 



Comanchic. 



Fig. 1412. Phylloceras knoxvillense, shell X K> ^^^^ septum. This is inverted, and 

 the finer divisions of the saddle are too narrow. (After Stanton.) 



Large ; in general form like the preceding, with small umbilicus ; 

 surface only with fine, forward curving striae; the internal mold 

 shows occasional sharp constrictions. 



Knoxville of California, etc., and of Queen Charlotte Islands 

 (Queen Charlotte formation). 



271. P. onoense Stanton. Comanchic. 



Like P. knoxvillense but more compressed, without constrictions 

 and with finer surface sculpture. 



Horsetown formation of Shasta County, California. 



