PLATE XXI. 



Page. 



Figs. 1-6. OioNioLOBOfERAS wei.i.kki Smith, sp. ikjv 125 



Natural size. 



Fig.". 1 and 2. Early adolei^cent stage, with roumled aljilonien. 



Figs. 3 and 4. Adult stage, with angular and slightly furrowed abdomen. 



Fig. .5. External septa. 



Fig. 6. Internal septa. 



Figs. 7-9. (i.\sTRiocEKAs ciLOBULOsuM Meek and Worthen ^i' 



Figs. 10-13. Schistoceras hyaiti Smith 10^ 



Fig. 10, a and b. (iastrioceran stage, 4 times enlarged; diameter 5.5 mm. 



Fig. 11, a, b, and c. Paralegoeeran stage, 4 times enlarged; diameter 10.5 mm. 



Fig. 12. Septa transitional from paralegoceran to schistoeeran stage; diameter 21 mm.; 



twice enlarged. 

 Fig. 13. Adult septa, diameter 42 mm., natural size. , 



Figs. 14-16. Popanoceras ganti Smith, sp. nov 132 



(The details of the internalsepta, fig. 16, could not be made out.) 



Figs. 17-19. Agathicer.\s ciscoense Smith, sp. nov 131 



Fuis. 20-22. ScHUCHEfiTiTES grahami Smith, sp. nov 50 



XoTE.— All specimens on this plate from the Upper t'oal Measures, Cisco formation, Graham, 

 Young County, Tex. 



190 



