1 82 NORTH AMERICAN INDEX FOSSILS. 



CXXXIII. Lytoceras Suess. 



Discoidal, widely umbilicated, scarcely, or but slightly, embrac- 

 ing; sections of whorls approaching circular; surface with lines of 

 growth, fine distant ribs, and often with constrictions in the inter- 

 nal molds; suture complexly incised, consisting of siphonal and 

 antisiphonal lobes and two lateral lobes ; the antisiphonal narrow, 

 with cruciform branches and ending in points; the siphonal lobe 

 is shorter than the first lateral one and is divided by a narrow, 

 pointed saddle. Jurassic-Cretacic. 

 305. L. batesi Trask. (Fig. 1439.) Comanchic. 



Fig. 1439. Lytoceras batesi, with cross section of last whorl, X %^ suture enlarged. 

 (After G abb.) 



Very slightly embracing, nearly circular whorls ; surface orna- 

 mented by fine, sharp, elevated ribs extending obliquely forward 

 over the venter, and sometimes by fine, spiral lines ; siphonal sad- 

 dles smooth. 



Knoxville beds of California, Oregon and Queen Charlotte 

 Islands. 



