CEPHALOPODA— AMMONOIDEA. 205 



357. H. (Bostrychoceras) elongatum Whiteaves. (Fig. 1473.) 



Cretacic. 

 Sinistral (left-handed) or dextral coil of round whorls in con- 



FiG. 1473. Helicoce7-as elongatum. (After Whiteaves, Mes. Foss. , I.) 



tact, with narrow umbilicus, sharp, simple ribs, and wide, concave 

 interspaces but no nodes ; last portion loose. 

 Nanaimo of Vancouver. 



CLIX. ExiTELOCERAS Hyatt. 



Helicoceran shells of low spire, with costae and two rows of 

 tubercles, each costa being tuberculated ; suture varying in com- 

 plexity; gerontic stage probably with retroversal living chamber. 

 Cretacic. 



358. E. jenneyi (Whitfield). (Fig. 1474.) Cretacic. 



Spiral coil low, ribbed, adult departing more strongly from 

 spiral curve; -costse sharp, distant, with occasionally shorter ones 

 intercalated; nodes in a continuous row on each side of depressed 

 venter; suture complex. 



Pierre group of the Black Hills. 



