391 Costa Rica Miocene — Olsson 219 



'i^ot Echinochana antiquata Maury, 1917, Bull. Amer. Pal., vol. 5, p. 

 365, pi. 33, fig. 10. E. yaquensis Maury. 



This species described by Dall from the Bowden beds of 

 Jamaica differs from the common, recent arcinella Linne of the 

 West Indies, by its more numerous, irregular and lower ribs 

 which bear only small, short spines. In arcinella the middle 

 ribs are heavy and bear large, stump-like spines and the wide 

 interspaces are reticulated with a coarse, mesh-like sculpture. 

 Gatun Stage: Middle Creek, 



Coll. 6, Old Man Sam Creek. 



Hill No. I, Banana River. 



Rio Blanco. 



Echinocama yaquensis Maury Plate 28, figure 5 



Chania arcinella Moore, 1853, Quart. Journ. Geol. Soc. L,ondon, vol. 



9, p. 130. Not of Linne. 

 Chania arcinella Gabb, 1873, Trans. Amer. Phil. Soc, vol. 15, p. 



251. 

 Chama arcinella Guppy, 1S74, Quart. Journ. Geol. Soc. London, vol. 



32, P- 531- 



Echinochama antiquata Maury, 191 7, Bull. Amer. Pal., vol. 5, p. 365, 



pl- 33. fig- lo- Not of Dall. 

 Echinochama antiquata vax. yaquensis Maury, 191 7, op. cit. p. 365, pi. 



33, figs. II, 12, 



Echinochama trachydervia Pilsbry and Johnson, 1917, Proc. Acad. 

 Nat. Sci. Phila., p. 197. 



The Echinochama yaquensis Maur}- from the Miocene of 

 Santo Domingo, where it is the prevaling species, differs from 

 the antiqiiata by the reduced number of its ribs, which in some 

 cases are nearly obsolete and in having its surface covered with 

 a coarse, mesh-like sculpture of raised pustules. 



In Costa Rica, the antiquata is the common species, but we 

 have also a single species of yaquensis collected from the lower 

 Gatun near Old Harbor. 



