321 



Costa Rica Miocene— OivSson 



149 



Turritella mimetes Brown and Pilsbry Plate 14, figure 5 



Turritella mimetes Brown and Pilsbry, 191 1, Proc. Acad. Nat. Sci. 



Phila., vol. 63, p. 357, pi. 27, fig. I. 

 Turritella {Hatistator) a.^. Han ley an a Reeve- T. lineolata (Kiener) 



Toula, 191 1, Jahrb, der K-K Geol. Reiclisanstalt, vol. 61, p. 



401, pi. 30, figures 6a and 6b, 



A large, robust species in form and sculpture like the T. 

 variegata Linnaeus, recent in the West Indies. 



The whorls are straight and usually slightly overhanging 

 the lower sutures. Surface sculptured with primary, secondary 

 and tertiar)^ spiral threads. The primary threads are irregularly 

 disposed and usually number about 7 or 8 to each whorl. Be- 

 tween the primaries are the finer secondaries and tertiaries. 



Small shells may be mistaken for the gatiinensis, but the 

 whorls are flat, without the median concave and constricted zone 

 and the sculpture is more coarse. The figured shell of 14 whorls 

 has a length of 70 mm and a diameter of 18 mm. A larger but 

 more imperfect specimen of but 4 whorls measures: 

 Length 50, diameter 20 mm. 



Gatun Stage: Gatiin, C. Z. 



Turritella altilira Conrad, and varities. 



Turritella attilira Conrad, 1857, Pacific R. R. Reports, vol. 6, p. 72, 

 pi. 5, fig. 19. 



Turritella gahbi Toula, 1909, Jahab. der K-K Geol. Reichsanstalt, p. 

 695, pi. 25, fig. 5. 



Turritella altilira Brown and Pilsbry, 191 1, Proc. Acad. Nat. Sci. 

 Phila., vol. 63, p. 358, pi. 27, figs. 2, 3. 



Of the Species of Tiirritella in the Gatun beds of Costa Rica 

 and Panana, the T. altilira of Conrad and its varieties is the most 

 common and characteristic. The T. tornata Guppy, from the 

 Miocene of Trinidad and Venezuela is a closely related species. 



These magnificent TurritellcE are preminently characteristic 

 of the West Indian and Caribbean Miocene, but probably deriv- 

 ed from earlier forms in the Oligocene. The stock continued in- 



