PLATE 38*. 



Pagd 

 Fig8. 1-11. SPIRIPERA MEDIALI8 227 



1. Dorsal valve of a small specimen, with extended cardinal extremities and Bne plications. 

 2-4. Dorsal, ventral and cardinal views of an extended form, having a high, nearly vertical, 

 cardinal area and narrow deltidial opening. 



6, C. Dursal and cardinal views of a s|)ecinicn of medium size, having fine plications, a high 



area, and extended cardinal extremities. 



7. Dorsal valve of a sjK'cimen having a triangular form, fVom the great extension of the hinge 



line. This is a somewhat unusual form. 

 8 - 11. Dorsal, ventral, cardinal and profile views of a narrow ventricose form, having a semi- 

 circular outline, and a high, almost vertical area. The surface is strongly marked with 

 concentric lines of growth. 



Figs. 12-18. Spirifera MEDiALis var. BATONi 22!> 



12- 15. Dorsal, profile, cardinal and front views of a specimen of medium size and ventricose 



form, characteristic of this variety. 

 16- 18. Dorsal,, cardinal and front views of a larger and somewhat unsymmetrical specimen. 



Figs. 19 - 22. Spibifsra hedialis var 227 



19. Cardinal view of a ventral valve with a high vertical area. 



20. Cardinal view of a still narrower form which is somewhat distorted. The area is vertical 



and the foramen very narrow. 



21. 22. Ventral and cardinal views uf an exfoliated specimen, having very fine plications and 



high area, which is somewhat receding towards the ai>ex; from limestone in the Uamil- 

 ton shales, at Eighteen Mile Creek, shore of Lake Erie. 



Figs. 23-32. Spirib'era angusta 23<i 



23, 24. Dorsal and ventral views of a young individual of a short form. 



2o-27. Dorsal, ventral and cardinal views of a larger specimen, having the hinge line more 



extended. 

 28-81. Dorsal, ventral, cardinal and profile views of a large specimen with extended cardinal 



extremities and a high sloping area. 

 32. Ventral view of a cast of a specimen with a short hinge line and rounded fVont margin. The 



mucronatc extensions of the hinge are so nearly solid that the filling of these portions of 



the shell is rarely preserved in casts, and owing to the loss of this part they appear to 



have a shorter hinge line. 



