333 



Costa Rica Miocene — Olsson 



i6i 



The smaller forms of Phasianella^ of which there are 2 or 3 

 species along the northern Costa Rican coast, are often extreme- 

 ly abundant on the rocks and reefs exposed to the heav3^ pound- 

 ing surf. There they are associated with a host of other gas- 

 tropods, principal among which are several species of Nerita^ 

 Fissurella, Purpura and Chitons. The fossil shells therefore like 

 the preceding Neritina viridemaris and several others which we 

 have already called attention to, have drifted frojii some near-by 

 rocky coast. 



Gatun Stage: C oil. 5, Red Cliff Creek. 

 Middle Creek. 



Genus TURBO Linnaeus 

 Turbo saltus, n. sp. Plate 15, figure 12 



Shell perforate, ovate- conic; spire high of about 6 convex 

 whorls, separated by deep, canaliculate sutures; the last whorl is 

 large and perfectly convex in form; sculpture consists of irregu- 

 lar, spiral cords or lirse; the earliest spire-whorls are strongly 

 carinated by a single, strong spiral, above and below which the 

 whorl is smooth; a second spiral appears above and the succeed- 

 ing whorls of the spire have 2 principal spiral cords or lirse, and 

 9 smaller ones; the last whorl has three spirals that are a little 

 stronger and many smaller ones of different sizes; the spirals are 

 smooth; aperture perfectly circular, a small, spreading callus on 

 the body-whorl just above the perforate base. 



Height 17, diameter 15.5, aperture 7.5 mm. 



Among the recent species of Turbo the saltus is related to 

 the large T. Spenglerianus Gmelin,onone hand and to the small- 

 er T. filosus Kiener on the other. The shell is perforate, in which 

 character it approaches T. filosus, but the sutures are canalicu- 

 late or channeled as in the non-perforate T. Spenglerianus. The 

 sculpture consists of irregular, smooth spiral cords or lir^e of 

 which 2 or 3 about the middle of the shell are a little larger 

 than the others. 



