CEPHALOPODA— ORTHOCHOANITES. 



109 



139. C. suciensis Whiteaves. (Fig. 1338.) Cretacic. 

 Differs from the preceding in having fewer, coarser, more dis- 

 tant and more curving ribs. 



Nanaimo group of Vancouver Islands. 



140. C. elegans Sowerby. (Fig. 1339.) Cretacic. 



Fig. 1338. Cymatoceras suciensis, 

 cross section, X %• (After Whit- 

 eaves. ) 



Fig. 1339. Cyjnatoceras elegans, X Yz' 

 (After Stanton.) 



Subglobose, of broadly rounded, transverse whorls; umbilicus 

 closed in young but slightly open in adult; costae broad, flattened, 

 about five times as broad as interspaces ; marked by growth lines. 



Benton shales of Missouri, similar horizon in Texas. 



Pleuronautilida. 



LIIL Proclydonautilus Mojsisovics. 



Strongly involute nautilicones, with rounded whorls, nearly cen- 

 tral siphuncle and strongly lobate sutures ; the abrupt ventral saddle 

 divided by a median lobe ; lateral lobe broad and deep. Triassic. 



141. P. triadicus Mojsisovics. (Fig. 1340.) Triassic. 



Umbilicus closed; umbilical shoulders broadly rounded; adult 

 whorls slightly broader than high ; surface marked only by growth 

 lines. 



Upper Triassic of Shasta County, California, abundant. Also 

 European. 



