PLATE VI. 



Trocholites multicostatus, Whitfield, Sp. (page 36). 



Figure 1. Side view, taken from a guttarpercha impression of a natural 

 mould of the exterior collected at Durham. 

 " la. Septum of the same species, showing the position of the si- 

 phuncle. 



Orthoceeas Darwini, Billings (page 38). 



Figure 2. The type of the species, from New Hope, which is laterally and 

 abnormally compressed. 

 " 2a. Smaller end of the same specimen, to show the outline of a 

 transverse section at that point. 



Ctrtoceras Mtrioe, Hall & "Whitfield (page 39). 



Figure 3. Specimen from Durham, for comparison with the preceding 

 species. 

 " 3a. View of a septum from the middle of the same specimen, which 

 shows the size, shape and position of the siphuncle. 



AscocERAS TowNSENDi (page 41). 



Figure 4. Side view of a cast of this species, from Durham. 

 " 4a. View of smaller end of the same, to show the position of the 

 siphuncle. 



