PLATE 116 . 
1-4. Platycehas nodosum. 
1 & 2. Casts of this species, preserving the usual form. 
3 & 4. View of the upper and lower side of the cast of a large individual. In this specimen, 
the nodes, either from weathering or extreme age and thickening of the shell, are less 
prominent than in the preceding. 
