PLATE I. 



Maclurea Logani (page 7). 



Figure 1. Maclurea Logani. Natural size. Lower or umbilical surface. 

 " 2. A younger specimen, with the operculum in place. 

 " 3. Upper view of same specimen, shewing the false umbilicus or 



concealed spire. This specimen has suffered some injury, and 



has a deep concentric furrow. 

 " 4, 5, 6. Exterior, inside and lateral views of an old operculum, with the 



apophyses for muscular attachments, a, b. 





