PALEONTOLOGY. 

 PLATE IV. 



Page. 

 Avicula (Oxytoma) mucronata 357 



Fig. 1. View of a left valve partly restored, showing the usual form of the specimens. 

 Fig. 2. View of the right valve enlarged to twice the natural size, posterior margin re- 

 stored to correspond with the lines of growth. 



Gervillia recta ..'. 358 



Fig. 3. View of a left valve, natural size. 



Camptonectes extenuatus 353 



Fig. 4. View of a very large left valve of the species from a locality east of Belle Fourche. 

 Fig. 5. View of smaller specimen, from the same lcoality, from which the surface shell has 

 been Temoved, the condition in which they are usually found. 



Camptonectes bellistriata 351 



Fig. 6. View of a right valve, the surface partially exfoliated. From Belle Fourche. 



Fig. 7. View of a left valve, imperfect on one side, showing the surface striae. From Belle 

 Fourche. 



Fig. 8. View of the interior of a large right valve from Big Horn Mountains, showing 

 the features of the type form of the species. 



Fig. 9. Exterior of a left valve, showing the surface striae. 



Fig. 10. Exterior of a right valve ; no striae are visible on the specimen, whether from exfo- 

 liation or naturally so is not readily determined. All right valves seen have 

 the surface smooth. 



Fig. 11. Enlargement of the surface as seen on specimens Figs. 6, 9. 



Pecten Newberryi 350 



Fig. 12. View of a left valve, imperfect on the anterior side of the cardinal line. 

 Fig. 13. View of another individual, showing the entire form. 

 Fig. 14. Enlargement of the surface, showing the elevated concentric striae. 

 Fig. 15. View of a right valve associated with the preceding, and supposed to be of the 

 same sx^ecies. 



