EXPLANATION OF PLATE LI I. 



Page 



FIG. 1. Igoce:as capulus . 1 



la. View from above. (Rowley collection.) 

 Ib. Outline from side. 



Carboniferous, Burlington limestone. 



FIG. 2. Igoctras fissurella 186 



Side view. (Keyes collection ) 

 Carboniferous, Keokuk limestone . 



FIG . 3 . Igoceras pabulocrinus 



Specimen attached to Platycrinus hemisphericus . (Keyes collection.) 

 Carboniferous, Keokuk limestone. 



FIG. 4. Plevrotomaria sp ? 



Side view. (Rowley collection ) 

 Carboniferous, Burlington limestone. 



FIG. 5. Pleurotomaria sp 1 

 Side view 

 Carboniferous, Burlington limestone. 



FIG . 6 . Strophostylus peoriensis 197 



Apertural view. (Keyes collection.) 

 Carboniferous, Coal Measures. 



FIG . 7 . Phanerotinus paradoxus 164 



Lateral view. 



Carboniferous, Burlington limestone. 



FIG . & . Maclurea magna (young) ? 163 



9a. View from above. (Mus. Mo. Geol. Sur.) 

 9b. Apertural aspect of same. 

 Silurian, Trenton limestone. 



FIG. 10. Capulus equilateralis 178 



lOa. Lateral aspect. (Keyes collection.) 



lOb. Apertural aspect of a specimen which, was probably attached to a Platycrinus. 

 Carboniferous, Keokuk limestone . 



