EXPLANATION or PLATE XXXVIII. 



Page 



FIG. 1. Productus lavicostus 44 



la. Ventral aspect. 



Carboniferous, Kinderhook shales. 



FIG. 2. Chonetes ornata 



2a. Ventral view. 



Carboniferous ?, Louisiana (Kinderhook) limestone. 



FIG. 3. Chonetes genicula 53 



Specimen enlarged two diameters. 

 Carboniferous?, Louisiana (Kinderhook) limestone. 



FIG. 4. Productella pyxidata 52 



4a. Ventral aspect of a smooth variety. 

 4b . Dorsal view of smooth shell . 

 4c. Ventral aspect of a ribbed shell. 

 4d. Ventral view of subspinous variety. 



Carboniferous?, Louisiana (Kinderhook) limestone. 



FIG. 5. Orthis swallowi 63 



View of a large example. 

 Carboniferous, Burlington limestone. 



FIG 6. Orthis iowensis 62 



6a. Side view. 

 6b. Doreal aspect. 

 6c. Ventral valve. 



Devonian, Callaway limestone. 



FIG. 7. Orthis bur ling tonensis 63 



A mature individual. 



Carboniferous, Burlington limestone. 



FIG. 8. Streptorhynchus crenistria 67 



8a. Ventral valve, exterior. 

 8b. Dorsal valve inbide. 

 8c. Dorsal valve, outside. 

 8d. Ventral valve, Interior. 

 8e. Ventral aspect. 

 8f. Dorsal valve, inside. 

 83. Ventral valve, inside. 

 8h. Dorsal aspect . 



Carboniferous, Upper Coal Measures. 



