■J 2 Palaeontographica Americana 



PI.ATB II 



Figure Page 



1. Area aqicila Heilprin lo 



After Heilprin. 



2. Area agui/a Heilprin; "Caloosahatchie beds; 1011.33.5 mm"; after Dall. 



3. Area boii'deniana Dall 11 



"Oligocene of Bowden, Jamaica; 11 mm"; after Dall. 



4. Area barbata Linne 12 



Recent from the Mediterranean. 



5. Area barbata Linne; recent from the West Indies; left valve; X 2. This is the form 

 common in the West Indies enlarged to show the grouping of the ribs. 



6. Interior of the right valve ; X 2 . 



7. Umbonal view of the same, natural size. Most of the ligament is broken off. It 

 did not extend ahead of the dark line just behind the beaks, though in larger indi- 

 viduals it may extend farther forward. 



8 . A rea eueulloides Conrad 13 



Jackson Eocene of Texas. An unlisually large specimen, showing the serrated 

 umbonal ridge. With age the ribs become more divided except on the posterior 

 slope, where they tend to disappear, leaving the shell nearly smooth. 

 g. Area eueulloides Conrad; Jackson Eocene of Louisiana, one mile above Gibson's 

 Landing. To show the well-sculptured, simpler ribbed young. The posterior rib- 

 bing is observed by the light. 



10. Interior of the same, enlarged. To show the entire teeth and crenulate margin of 

 the young. 



11. A rea eueu/Zoides Conrad; Jackson Eocene of Jackson, Mississippi. Adult, with ir- 

 regular teeth. This figure shows the characteristic cardinal area of Calloarea with 

 close, even grooving. 



12. Exterior of the same. 



