PLATE 48. 



rage 



Figs. 1-25. Meristella nasuta -iSMl 



1. The cast of a large dorsal valve. 



2. The caNt of an imperfect specimen of the dorsal valve, showiug mure distinctly the muscular 



impressions. 



8,4. Cast of ventral valves of an elongated form, with deep muscular impressions. 



6, 6. Casts of ventral valves of larger individuals, .showing somewhat different forms of muscu- 

 lar impressions. The above are from tlie Schoharie grit. 



7-9. Dorsal, ventral and profile views of a young individual of a lenticular form, which is not 

 produced in front. 



10. A small elliptical form which is produced in ft-ont. 



11, 12. Dorsal and profile views of a larger and proportionally shorter form than fig. 10. 

 lo. A front view of a specimen, showing an extreme elevation of the ventral valve. 



14. Dorsal view of a broad form of the species. 



15, 16. Dorsal and ventral views of a large individual of a broadly oval and somewhat quadri- 



lateral form. 



17. The interior of a dorsal valve, showing the hinge plate and muscular impression. 



18. The interior of an im|)erfect ventral valve. 



19. Dorsal view of a specimen, showing the internal spires and median septum. 



20. 21. Dorsal and profile views of a cast in cliert, from the Corniferous limestone. 



22. The cardinal view of another cast, showing the muscular impressions, the filling of the ros- 

 tral and teeth cavities, and the spaces left by the removal of the dental lamella;, liinge 

 plate and median septum. Figs. 7-22 are of specimons from the Upper Helderberg 

 limestones. 



2.3 - 25 Dorsal, profile and ventral views of a large individual, which is much produced in front 

 and having a comparatively shallow dorsal valve; from the Schoharie grit. This is the 

 form originally described as Meristella elista. 



