385 



Costa Rica Miocene — Olsson 



213 



Gatun Stage: Water Cay. 



Old Man Sam Creek, Coll. No. 6. 

 Bana?ia River. 



Subgenus CRASSINELLA, Guppy 



Crassatellites bowdenensis Dall, variety costaricensis, n. var. 



Plate 29, figure 12 



Cf. Crassatellites [Crassinella) bowdenensis Dall, 1903, Trans. Wagner 

 Free Inst. Sci., vol. 3, pt. 6, p. 1476, pi. 50, figs. 2, 3. 



Shell small, triangular, slighth^ convex, subequilateral, the 

 anterior end generally a little longer and more pointed; beaks 

 triangular, slightly pointing forwards; lunule large, narrowh^ 

 lanceolate, smooth; escutcheon small; surface sculptured with 

 small, even, concentric riblets which on some shells ma}^ be 

 strong and persistent over the greater part of the shell , or on 

 some specimen sub-obsolete; interior of shell cavity shallow^ with 

 a moderately heavy hinge. 



Length 3.00, height 2.75, diameter .75 mm. 

 3-50, 3-50, -75 nim. 



The typical bowdenensis Dall from the Bowden Miocene of 

 Jamaica is a more solid, more convex and triangular shell. The 

 variet}^ costaricensis is very abundant at several localities in Costa 

 Rica in certain horizons. The sculpture varies from strong, 

 even, concentric riblets covering the greater part of the shell, to 

 forms which are nearly smooth. 



Gatun Stage: Hill la, Banana River. 

 Middle Creek. 

 Zo7ie Quitana Creek. 



Crassatellites midiensis, n. sp. Plate 29, figure 11 



Shell small, trigonal, slightly convex and equilateral; the 

 beaks are central and erect; the dorsal margins straight and 

 meeting at the beaks nearly at right angles; the surface is sculp- 

 tured with subregular, distant, concentric lamellae-like riblets, 



