MOLLUSCA — CEPHALOPODS 



267 



5. Distinguish the ammonitic type of suture from the goni- 

 atitic ; give examples of each. 





Fig. 119. — Scaphites nodosus, var. hrems Meek. An entire shell from the Pierre 

 (Cretaceous) of Montana. A, view of opening of hving chamber ( X f ). B, side 

 view. C, the suture (X I2) extending from the position of the siphuncle (upon 

 the outer edge of the coil) to the unbilicus (umb.). si., siphuncle. (From Meek.) 



Baculites (Fig. 120). Cretaceous. 



Straight (except, the first-formed part, \vhich is spiral), ellip- 

 tical in section. Sutures with the lobes symmetrically divided. 

 Named from its shape, from Latin baculum, a staff, + ites, 

 meaning stone. 



B. compressus is abundant, associated both east and west 

 with the variety of Scaphites noted above and with several 

 species of the pelecypod Inoceramus. 



