' 60- 



ten trajaslucent ; the left valve inflate'', the right- flattened; mn- 

 "bones central, almost 'biit not quite terminal ; exterior surface usu- 

 ally' smooth, with a fevf e" agger? -f^e " p-rov;th lines, sometimes deli- 

 cjstely wrintlel; interior of valves possess the eharaoters of the 

 gen-s." (Goiiia, 1841). 



_Hemar]£S.- Host of the Bovt'^^-'^ -^^ -"'^esentatives of this genus 

 are, es state" ahove, referred to siraplex * Ihej' possess the accept- 

 ed diagnostic fea^^ure oT this protean form - the smooth exterior 

 surface. ITone of them exceed 17 nun. in latitude or altitude. As 

 would he ex"Dected among small forms, the grov/th lines are not 

 Gonspicuouslj? emphasized. 



Gupioy and Dall reporte"' this species from the "Oli-ooene of 

 Jamaica" in 1896, but it does not apoear in the 190?) check list. 

 At least some of C-ahh's Ganto Domingisn ephippium appear referrahle 

 to this species. Toula has merely mentioned the presence of a 

 "kleinen dilmisch;~ligen bltitterigen Anomia " in the Gatun fauna. 



Occurrence .- Oligocene: 3anto jJomingo (Gahb, 1872); 

 lo^^er I'lioG ene : 3o',"den beds, 3owden, Jamaica ( Guppj- and Dall, 1805); 

 Kiocene : Calvert formation, Virginia (Gardner, Hss.), St. Llary's 

 formation, L'-aryland (Glenn, 1304), Vir^^-inia (Gardner, I.Tss.), 

 Yorktov/n formation, Yirprinia (Gardner, lusrs.), Duplin formation, 

 ITorth Carolina (auetores), Choctawhatchie marl, "Florida (Gardner, 

 Hss. ) ?liocene: I-'ashua marl, i^orth Carolina, (Gardner, liic). 



