EXPLANATION OF PLATES. 197 



PLATE VI. _ 



LiNGULA MOSIA. [^ < / t ^ 



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

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



LiNGULA AURORA. A . / 1 (/f 



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

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

 exiremitv. 



LiNGULA AURORA, iff?'. ^ ^ 



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

 '« 7. A cast of the interior of a ventral valve of tliis species. 

 «« 8. An enlargement of the surface, showing the regular concentric lines of gi"oi 

 and the undulating lamellose striae, which, crossing the lines of g« 

 give the apparently punctate texture. 



LiNGULA WINONA. ') ,11^ 

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



LiNGULA AMPLA. , / :? 5"" 



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



DiSCINA? INUTILIS. / 3 



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. 



LiNGULEPIS PINNAFORMIS. ^->I'' 



Fig. 12 & 13. Two forms of the shorter valve, which have been referred with doubt to 

 this species. 



<* 15. An enlargement of the cast of this valve, showing a flabelliform muscular 

 impression. 



<• 14. An elongate spatulate valve, which has the typical form of Dr. Owen's species. 



♦♦ 16. An enlargement of the cast of a similar valve, showing the tripartite muscu- 

 lar impression. •♦■;.- 



Obolella? POLITA. /5 c!) 



Fig. 17. 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. 



•« 21. The dorsal? valve, enlarged as the preceding, showing the muscular impres- 

 sions with larger bosses or articulating surfaces of the cardinal line. 



Fig. 22. A brachiopod having the form of Strophomena or Strophodonta, but its 

 generic relations are not determined. 



Orthis PEPINA. / ^ -^ 



Fio. 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. 



