PALEONTOLOGY. 

 PLATE II. 



Page. 

 LlNGULEPIS PINNAFOKMIS 335 



Figs. 1, 2. Views of the dorsal and ventral valves of the ordinary form from the greenish 

 purple sandstone at the headwaters of Eed Canon Creek, southwest of the 

 Black Hills. 



Figs. 3, 4. Views of two specimens, dorsal valves, from the friable sandstones of Castle 

 Creek, west of the Black Hills. 



LlNGULEPIS CDNEOLUS 336 



Figs. 5, 6. Enlarged views of what are supposed to be the dorsal and ventral valves. 



LlNGULEPIS PERATTENUATUS 337 



Figs. 7, 8. Views of two dorsal valves, showing a slight variation in form. Enlarged. 

 Fig. 9. Enlarged view of a ventral valve. 



LlNGULEPIS DAKOTENSIS 337 



Figs. 10, 11. Copies of Mr. Meek's figures, showing ventral valves of this species. 



Obolella polita 339 



Fig. 12. Enlarged view of a dorsal (?) valve. 



Fig. 13. Enlarged view of a ventral valve, showing the prolonged beak. 



Or.OLELLA NANA 340 



Fig. 14. Enlarged view of a specimen of the broad oblate form. 



Fig. 15. Enlargement of a more circular specimen. 



Fig. 16. Enlargement of an elongated specimen. This and the specimen Fig. 14 show the 



extremes of variation among the specimens on one block of sandstone. 

 Fig. 17. View of the interior, enlarged. The figure is a copy of that given by M. & H., 



Pal. Upp. Missouri, Plate 1, Fig. 3. 



OBOLUS ? PECTENOIDES 338 



Figs. 18, 19. Enlarged views of two valves, one of which retains the shell almost entire 

 and the other exfoliated,. showing tbe radiating lines. 



Crepicephalus planus.. 343 



Fig. 20. View of the specimen described, showing the characters as given. 



Ceepicephalus centralis 341 



Fig. 21. View of the glabella and fixed cheeks of a large individual, showing the broadly 



conical form. 

 Fig. 22. View of another individual, showing the narrow form of glabella. 

 Fig. 23. Profile view of tbe last specimen, showing the elevation and curvature of parts. 

 Fig. 24. View of an imperfect cheek referred to this species, being associated with it on tho 



same block. 



Aeenicolites sp. 1 333 



Fig. 25. View of the specimen from Warren Peak, showing the form, relative size, and 

 direction of the tubes. 



