PLATE XI. 



Page. 

 Figs. 1-4. Gasteioceras oarbonarium von Buch 84 



Middle Coal Jleasjures, near Boles, Scott County, Ark. 



Fig. 1. Side view of a composite artificial cast, from three specimens. 



Fig. 2. Side view of a septate fragment. 



Fig. 3. Cross section of whorl. 



Fig. 4. Sutures. 

 Figs. .5-7. Pronorites siebexthali Smith, sp. nov 47 



Middle Coal Measures, near Boles, Scott County, .\rk. 



Fig. 5. Side view of septate fragment. 



Fig. 6. Cross section of whoi-1. 



Fig. 7. Sutures. 

 Figs. 8-13. Ga.strioceras branneri Smith 83 



Lower Carboniferous, Chester stage, Pilot Mountain, Carroll County, Ark. 



Fig. 8. Side view. 



Fig. 9. Front view. 



Fig. 10. Rear view. 



Fig. 11. Cross section. 



Fig. 12. Sutures of adult, twice enlarged. 



Fig. 13. Suture.s! at diameter 23 mm., twice enlarged. 

 Spec. Nat. Mus. 



Note.— Figs. 1-7 formed PI. XX, Proc. Am. Philos. Soc, Vol. XXXV. 



Figs. 8-13 formed part of PI. XXIIl, Proc. Am. Philos. Soc, Vol. XXXV. 



170 



