EXPLANATION OF PLATE XL1X. 



Page 



FIG. 1. Pleurotomaria missouriensis 136 



Another view of specimen shown on preceding plate. 



FIG. 2. Pleurotomaria subcarbonaria 335 



2a. Type specimen (Kowley collection.) 

 Carboniferous, Burlington limestone. 



FIG . 3. Murchisonia melaniformis ? 145 



Side view. (Mus. Mo. Geol. Sur.) 



Cambrian ? 

 FIG. 4. Murchisonia terebra 146 



A somewhat worn specimen. (Hare collection.) 



Carboniferous, Upper Coal Measures. 



FIG. 5. Murchisonia major 145 



5a. Specimen with shell. (Mus. Mo. Geol. Sur.) 

 5b. Internal cast. (Same collection .) 

 Silurian, Trenton limestone. 



