2o6c Costa Rica Miocene — Olsson 34c 



Subgenus CYLICHNELLA, Gabb 



Acteocina triticum-tritonis Maury 



Cylichnella bidentata Gabb, 1873, (in part) Trans. Amer. Phil. Soc. , 



vol. 15, p. 273. Not of d'Orbigny, 1845. 

 Cylichna bidentata Guppy, 1876, Quart. Journ. Geol. Soc. London, vol. 



32, p. 518. 

 Acteocina {^Cylichnella) triticum-tritonis Maury, 1917, Bull. Amer. 

 Pal., vol. 5, p. 178, pi. 3, fig. 4. 

 This shell was separated by Dr. Maury from the recent bi- 

 dentata d'Orbignj^, with which Gabb, Guppy and others had 

 identified it. In triticum-tritonis the anterior of its plications is 

 very small, the posterior one large, which is the reverse of the 

 conditions as seen in the living bidentata. The base of the shell 

 is finely grooved with incised, spiral lines. The specimens from 

 Costa Rica agree very closely with typical specimens from the 

 Miocene of Santo Domingo. 



Gatun Stage: Middle Creek. 



Genus VOLVULA, A. Adams 



Volvula cylindrica Gabb 



Volvula cylindrica Gabb, 1873, Trans. Amer. Phil. Soc. vol. 15, p. 



246. 

 Volvula cylindrica Guppy, 1876, Quart. Journ. Geol. Soc. London, 



vol. 32, p. 518. 

 cf. Bulla ( Volvula) cf. oxytata Toula, 1908, Jahrb. der K-K. Geol. 



Reichsanstalt, Wien, vol. 58. p. 709, pi, 28, fig. 4. 

 Volvula cylindrica Maury, 1917, Bull. Amer. Pal., vol. 5, p. 180, pi. 3, 



fig- 5. 

 This, is a small species of no unusual characters. It is nar- 

 rowly cylindrical in form, shortly produced and pointed at its 

 posterior extremity. It was described hy Gabb from the Mio- 

 cene of Santo Domingo, but Dall united with it, the oxytata 

 Bush, in which case, it is also found in the recent fauna. Gabb 

 records acuta d'Orb. from the Pliocene of the lyimon Peninsula. 

 Uscari Stage: Middle Creek. 



Genus BULLARIA. Rafinesque 

 Bullaria paupercula Sowerby Plate 4, figure 14 



