Explanation of the Plates. 



PLATE I. 



LlNGULA 3I0SIA. 



Figs. 1, 2, 3. Varieties of form referred to this species, from Mazomania. 

 Fig. 3 a. A broadly ovate forcn of this species ? from Stillwater. 



LlNGULA AURORA. 



Fig. 4. A specimen showing the two valves slightly displaced. 

 " 5. A larger individual, probably the ventral valve, which is truncated at the extremity. 



LlNGULA AURORA, V(IV. 



Fig. 6. The exterior of this form, which is more nearly elliptical than the preceding. 

 " 7. A cast, of the interior of a ventral valve of this species. 



" 8. An enlargement of the surface, (of form like No. 5) showing the regular concentric lines 

 of growth and the undulating lamellose strias, Avhich, crossing the lines of growth, 

 give the apparently punctate texture. 



LlNGULA WINONA. 

 Fig. 9. A figure of the specimen, natural size. 



LlNGULA AMPLA. 

 Fig. 10. A figure of this species, of the natural size. 



Piscina? inutilis. 



Fig. 11. A figure of the specimen, enlarged two diameters. The substance of the fossil has been 

 partially removed, but the impression of the surface remains. 



LlNGULEPIS PINNAFORMIS. 



& 13. Two forms of the shorter valve, which have been referred with doubt to this species. 

 An enlargement of the cast of this valve, showing a fiabellifonn muscular impression. 

 An elongate spatulate valve, which has the typical form of Dr. Owen's species. 

 An enlargement of the cast of a similar valve, showing the tripartite muscular impression. 



Obolella? POLITA. 



Fig. IT. A figure of a specimen, natural size. 

 " 18. An enlargement of a specimen of similar form. 



" 19. A cast enlarged to the same degree as the preceding, and showing the cavities left by the 



articular bosses or muscular pads. 

 " 20. The interior of the ventral ? valve, showing the muscular impressions, with a sinus at 



the apex. The figure is greatly enlarged. 

 " 2L The dorsal ? valve, enlarged as the preceding, showing the muscular impressions with 



larger bosses or articulating surfaces of the cardinal line. 



" 22. A brachiopod having the form of Strophomena or Strophodonta, but its generic rela- 

 tions are not determined. 



Orthis pepina. 



Fig. 23. A dorsal valve, natural size. 

 " 24. A ventral valve, natural size. 

 " 25. A cast of the dorsal valve. 



" 26 & 27. Casts of the interior of the ventral valve, fig. 26 showing the vascular impressions. 



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