- S-">7- 



is larger, v.l fh fe'.ver, less oonspicnoiislj^ nodulated ribs and wider 

 intersnaces. The Santo Dominp-ian specimens reach a size lar^^er 

 th-sn. an 2,' of the _;o\vden ones. 



Oahh has criticized Gnppy's figure because of the pos ' 

 of the va^ve anc. use the 'iro-oer number of ribe is not shown. 



It should be added that the up-^er anterior r:arf-i-. ' lically not 



as angular as is indicated on the figure, and since, on the figure, 

 the terraces of the ribs are not differentiated from the nodulated 

 keel, '■' :'ibi3 are v^rider than they should be. 



Occurrence .- Upoer Oligocene : Santo Doninp-o (Gabb, 1873; 

 ^ruppy, 1874, 1076; D?ll, 1905)', Lower i.Iiooene: Bov;den beds. 



Bow den, Jamaica (Guppy, 1866, 1874; Ball, 1961.'?), 



