PLATE XXVI. 



PAGE 



Figs. 1-5. TuEEiTELLA MORTONi Conrad 147 



1. Ventral view of specimen. Potomac Creek, 

 la. Dorsal view of same specimen. 



2. More elongate specimen from same locality. 



3. Specimen from same locality with stronger basal carina. 



4. Internal cast. 



5. Specimen showing the strong basal carina of the variety postmortoni 



of Harris. Tinkers Creek. 



278 



