PLATE XXII b. 



Zone of Amaltheus oxynotus. 



Fig. 1. Arietites Collenottii, aVOrbigny. Side view, natural size. Woodwardian 



Museum, Cambridge. The lateral lobes 

 with their numerous digitations, and 

 the saddles with their lobules, are well 

 shown in sittl in this specimen, the 

 largest that has been found. 



2. — — Front view of same shell showing the 



sagittate aperture. 



3. — — Siphonal area, natural size, showing the 



form of the siphonal lobes filling in the 

 sulci. 



