359 



Costa Rica Miocknk — Olsson 



87 



{B) SUPER-FAMILY RHACHIGLOSSA 



Genus OLIVA Briiguiere 



Olives are among the most common fossils in the Miocene 

 beds of Panama and Costa Rica. The various species, however 

 show so few distinguishing characters, that their identification 

 becomes at times, both difficult and uncertain. The following 

 key has been prepared showing the characters which have been 

 most relied upon for their separation. This key should be used 

 in conjunction with the figures. 



A. Aperture narrow and of about the same wndth along its 

 whole length. Inner lip finely and regularly crenulated 

 above. 



B. Sutures deep or channelled, with the edge of the 

 whorl projecting slightly above; spire of medium 

 height, length 35 mm. 



O. sayana var. immortua Pilsbry & Brown 

 BB. Sutures not channelled and with the upper edge of 

 the whorl beveled or appressed. 



C. Spire generall}^ low^ with concave profile and 

 usually a projecting and globular nucleus. 

 Length 35 mm. O. brevispira Gabb 

 CC. Spire high or short, with conic sides; nu- 

 cleus or protoconch not large or prominent. 

 D. Spire high and conic; shell large. 

 Length 40 mm or more 



O. cylindrica Sowerby 

 DD. Spire short, shell usually small. Length 

 rarely over 30 mm. 



O. gatuncnsis Toula 

 A A. Aperture v/ide and usually expanded and flaring in 

 front; inner lip is not crenulated above. (Agaronia) 

 B. Spire long, about 1-3 of the length of the shell; 



