PLATE VI. 



Zone of Amaltheus oxynotus. 



Fig. 1. Arietites denotatus, Simpson. Lateral view. Natural size. The finest 

 specimen known ; from the Leckenby Collection, Woodwardian Museum, 

 Cambridge. 



2. Arietites nodulosus, Young and Bird= Arietites obesulus, Blake. Lateral 



view of a small perfect specimen, magnified two diameters, collected from 

 a brown sandy rock, Robin Hood's Bay. My collection. 



3. View of the siphonal area of the same shell, showing the line of tubercles on the 



margin, with the oblique-forward directed ribs arising from the tubercular 

 series. The outline of the foliations of the lateral lobes is well shown 

 in Fig. 2, and the siphonal lobes are remarkable for their great elonga- 

 tion, and are seen in Fig. 3, where the superior lateral, inferior lateral, and 

 auxiliary lobes are shown in situ. 



Zone of Arietites Bucklandi. 



Fig. 4. Arietites Brooki, Sowerby. Lateral view, natural size, of a very beautiful 

 Ammonite, with the shell-structure in fine preservation, and showing the 

 lines of growth on its surface. My collection. 

 5. Accurate outline of the foliations of Arietites Brooki from another specimen, as 

 none are visible in Fig. 4, in consequence of the presence of the shell all 

 over the mould. My collection. 



