CEPHALOPODA— BELEMNOIDEA 



Fig. 1 510. a, b, Pj-ionocyclus xvyomingensis^ fragment of a large specimen, X /^ J <^» 

 a small specimen, X K J ^' suture ; (?, /, P. tnacombi, X /^ 5 .^. suture. (After 

 Stanton. ) 



Subclass DIBRANCHIATA Owen. 



Order BELEMNOIDEA. 



Belemnitida. 



CLXXIV. Atractites Guembel. 



Belemnites with long phragmocone and short guard ; septa 

 simple, concave; siphuncle marginal, siphonal funnels marked; 

 protoconch calcareous. Triassic-Jurassic. 



404. A. phillippi Hyatt and Smith. (Fig. 151 1.) Triassic. 



Long and slender, circular in section ; guard thick and massive, 

 not extending far beyond the shell ; absent in young shells. 



Triassic of Shasta County, California. 



CLXXV. Belemnites Lister. 



Guard finger-like, cigar-shaped, subcylindrical or conoidal, some- 

 times short and thick, sometimes long and submucronate or ob- 

 tusely rounded, frequently with ventral furrow of greater or less 

 extent, and with dorsolateral grooves. Phragmocone generally 



