MOLLUSCA — CEPHALOPODS 



267 



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

 atitic ; give examples of each. 



c^;i 



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

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

 view. C, the suture ( X i^) 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, w*hich 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. 



