■7 _ 



Ox the lir-araent pit decidedly t hi cleaned axid posteriorly 

 forming a projecting process. 



Dimensio ns.- A right v^lve : Length, 8 ram.; alt., 7 mm.; 

 diara. , 3 mr.:. A left valve: Leno-ht , 5.5 mm.; alt., 4 mm.; diam. 

 2 mm. 



Hemarks.- Right valves of G_. h eterogena a re very abtmdant, 

 but, curiously enough, left valves are much less numerous. The 

 two can not be confused with the other Oorbulas, the right valves 

 being recognized b:. its high, narrov; outline and the left by its 

 more elon?rate ortline and radial sculpt:tre. Right valves dis- 

 play an inconstant outline, some being more oroduced posteriorly; 



the largest has the following dimensions: length, 8.5 mm.; alt., 

 7.5 mm.; diam., 4.5 mm. iTie average valve is higher and narrower 

 than the one figured b;; jail. Both sets of sculpture on the left 

 valve are usually obscure. Axi interesting feature is the decided 

 thicfeenin?? of the hinge-mar^^in on the left valve behind and luider 

 the ligament pit. 



The type of £. vieta is from the Socene of Kanzanilla, Trini- 

 dad, but ^uppy also reporte'' it from the "Upper I'iocene, Jamaica", 

 confusing it ^Tith the present species. In the 1896 notice of 

 Jintillean fossils Dall apparently consolidated both vieta and 

 the ^o-.vden form with the recent 0. disparilis d'Orbigny (l). 



(1). In de la Sagra, Hist., phys., polit. et natur., de 1 ' lie 

 de 'Juba I'ollusoues, vol. 2, p. 287^, pi. 27, firs. 1-4, 

 1853. (?rench ed). 



