PLATE XIX. 
I’age. 
Fig. 1. 2I(Bonia f/racilis, Z . D. — Lateral view of specimen ... ... ... ... 221 
Fig. 2. Pachydomus i)usiUus,V. McQoj — Internal cast, side view ... ... ... 217 
Fig. 2a. The same, seen from above ... ... ... ... ... ... ... ... 217 
Fig. 3. Pacliydomus ovaJis, F. McCoy — Internal cast, with a little of the shell preserved 216 
Fig. 4. Pachydomus poliUis, Z .Jy. — Internal cast, seen from the side ... ... 218 
Fig. 4«. The same, seen from above ... ... ... ... ... ... ... ... 218 
Fig. 5. L. G. de Koninck — Lateral view of specimen ... ... 218 
Fig. 5rt. The same, seen from above ... ... ... ... ... ... ... ... 218 
Fig. 6, Mceonia Koninclii, W. B. Clarke — Side view of a portion ... ... ... 219 
Fig. 0«. The same, seen from above ... ... ... ... ... ... ... ... 219 
Fig 7. PleuropJioi'us b/plex, h. G. de Koninck — Internal cast, lateral view ... ... 222 
Fig. 8. PleurjpJiorus carinafus, J . 'Movris — Internal cast, lateral view ... ... ... 223 
