EXPLANATION OF PLATE LXVIH. 



Pleuracanthm (? species). 



(All figures natural size.) 

 Figure 



1. Right lower jaw. Internal surface, 

 la. ,, ,, „ External surface. 



2. Articulating extremity of lower jaw. 



3. The same of another specimen. 



fl. Articulating process. 

 6. Angular bone, 

 c. Dentary bone. 



4. PUuracanthus {Diplodus) lavissimxts, Agass. Exhibiting the serial arrangement of the teeth. 



a. Teeth of upper jaw. 



b. Teeth of lower jaw. 



5, 5a. Osseous fragment, with articulating surface. 



6. Another example, with articulating extremity. 



7. Osseous plate. 



8. Occipital plate. 



9. Pterygopodium (clasper) of the ventral fin. 



a. Clasper. 



10. Pterygopodium, (?). 



Formation and Locality. — All ^except fig. 4 from Low Main Coal Seam, Newsham. Fig. 4, Thin 

 Bed Coal, Burnley, Lancashire. 



Ex coZL— Figs. 1, 2, 5, 6, 7, 8, 9, W. Dinnmg, Newcastle-on-Tyne ; fig. 3, Atthey Collection, 

 Museum, Newcastle-on-Tyne ; fig. 4, George Wild, Bardsley, Lancashire. 



18] 



