- 1 



-S 



ame 



and inflated form, thick shell and relatively high, imdivided ribs 

 separated by deeply channeled interspaces. Yourig individuals are 

 proporti-^nately less inflated than adTxlts and the umhonal snlciu 

 is often more prominent. A. inaegiiilateralis is of about the ss 

 size but Is much thinner^ more produced posteriorly, less inflated 

 and has finer ribs; A. per-ole ura i s hig-her, heavier, has fuller, 

 more prominent beaks, wider ribs and narrower interspaces. The 

 Ohipola A. hy come la Dall (1) has the same general form, but is much 



(1). Trans. .Vainer ?ree Inst. Sci,, Philadelphia, vol. 3, ot. 4, 

 pp. 657-638, pi. 33, fig. 1, 1898. 



larger and has lower, deeply sulcate ribs and a wider cardinal 

 area. 



This species is named for I'r. Stanley 7orden, of the Karyland 

 Geological Survey, '"'ho gave efficient assistance in the prepara- 

 tion and preliminary determii^iation of the material. 



Occurrence^. - Lower l.'iooene: Bov;den beds, Bowden, -Jamaica. 



