39 i Costa Rica Miocene — Olsson 219 



l^ot Echinockana antiguata Maury, 1917, Bull. Amer, Pah, vol. 5, p. 

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



This Species described by Dall from tiie Bowden beds of 

 Jamaica differs from tlie common, recent arcinella Linne of the 

 West Indies, hy 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 JVo. I, Banana River. 



Rio Blanco. 



Echinocama yaquensis Maury Plate 28, figure 5 



Chama arcinella Moore, 1853, Quart. Journ. Geol. Soc. lyondon, vol. 



9, p. 130. Not of L/inne. 

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



251. 



Chama arcinella Guppy, 1874, Quart. Journ. Geol. Soc. Ivondon, vol. 



32, p. 531- 



Echinochama antiguata Maury, 1917, Bull. Amer, Pal., vol. 5, p. 365, 



pi. 33, fig. 10, Not of Dall. 

 Echinochama antiguata \-a.r. yague?isis Momtj, 191 7, op. cit. p. 365, pi. 



33, figs. II, 12, 



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

 Nat. Sci. Phila., p. 197. 



The Eclmiochama yaquensis Maur}^ from the Miocene of 

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

 the antiquata 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 antiq2iata is the common species, but we 

 have also a single species of yaquensis collected from the lov/er 

 Gatun near Old Harbor. 



