CEPHALOPODA— AMMONOIDEA. 



157 



251. T. (Metatirolites) foliaceus Dittmar. (Fig. 1405, h-j.) 



Triassic. 



Venter broadly rounded, with sharply forward arching growth 

 lines; ventral borders marked by strong tubercles. 



Upper Triassic of Shasta County, California, and the Alps. 



CVII. Ceratites deHaan. 



Moderately involute ; whorls not deeply embracing, increasing 

 rather rapidly in diameter, thus causing umbilicus to widen ; sub- 

 quadratic in section, usually higher than wide, with square abdomi- 

 nal shoulders and flattened venter; surface with ribs, which begin 

 with nodes near umbilicus, and end in nodes at ventral margin; 



Fig. 1405. a-c, Ceratites humboldtensis^ side view and section X Vzi ^"^ suture; 

 d-g, C. {Gytnnotoceras) blakei, three views X %» ^"<i suture; h-j, Tirolites {^Meta- 

 tirolites) foliaceus, two views X %. ai^d suture. (After Hyatt and Smith. ) 



suture with rounded, generally entire saddles, and serrated lobes, 

 of which there are a divided external, two laterals and several 

 small auxiliaries. Triassic. 



252. C. humboldtensis Hyatt and Smith. ( Fig. 1405, a-c. ) Triassic. 

 Ribs curving, bifurcating; tubercles elongate; suture with 

 slightly notched or wavy saddles and principal lobes serrated. 



