PLATE XVIII. 



Page. 

 Ctlyphioceijas calyx Phillips 62 



Lower Carlioniferous St. Louis-Chester stage, ]Moorefield, Ark. 



Figs. 1-.3, Larval staije, diameter 0.98 mm., 20 times enlarged; oorresjioiiding to Puro- 



doceras. 

 Figs. 4 and 5. Early adolescent stage, corresponding to Prionoreran; liiameter L56 mm., 



If coils, 20 times enlarged. 

 Figs. t)-8. Later adolescent stage, transitional from Prionorerns to Ghiplnotxnix; diameter 



2.25 mm., 3J coils, 13 times enlarged. 

 Figs. 9-11. Mature stage, diameter 4.2.5 mm., 4i coils, 10 times enlarged. 



184 



