309 Costa Rica Miocene — Olsson 137 



body- whorl and a lower spire. The spire-whorls are striated but 

 the spirals are lacking from the generally polished body- whorl. 

 The aperture of laevigata is subrectangular in outline, rather 

 wide anteriorl}^ and flaring posteriorly, while in Gabbi, the aper- 

 ture is narrow and but little larger anteriorly. In laevigata, the 

 callus of the inner lip is large and spreads widely over the colu- 

 mellar area, but its outer edge is raised and shelf-like, instead of 

 rounded and appressed as in Qabbi. Mature shells of laevigata, 

 have three large, heavy varices, marking the resting stages but 

 such varices are small and sometimes entirely lacking from the 

 Costa Rican shells. 



Typical laevigata will probably be found to be largely limit- 

 ed to Santo Domingo. The ^qxq.s.\C2l sublaevigata (possibl^^ a var- 

 iet)'-) has more strongly sculptured whorls, a short spire and less 

 complete varices. Its aperture is that of true laevigata. 



The Sconsia laevigata was found by Dr. Maury, in her work 

 on the Paleontology and Stratigraphy of Santo Domingo to be 

 limited to her upper or Gurabo formation iX^^-Sconsia laevigata 

 zone) . In Panama and Costa Rica, the Sconsia laevigata variet}' 

 Gabbi, is frequently very abundant in the Gatun beds, but it is 

 apperently lacking from the underl3dng Uscari shales where it is 

 replaced by the new Scojisia cocleana and probably bocasensis. 



Gatun Stage: Gatuyi, C. Z. 



Toro Cay, Water Cay, Panama. 

 Coniadre Creek near Cahuita C. R. 

 Rio Bla7ico, C, R. 



Sconsia bocasensis, n. sp. Plate 12, figures 12, 13 



Shell like that of laevigata ,h\x\. narrow and with coarsely sculp- 

 tured whorls; spire more evenly conic, the apex of which is not 

 produced or attenuated; whorls coarsely sculptured with heavy, 

 persistent spirals threads, of which there are about 9 on the spire- 

 whorls and nearly 50 on the last whorl; sutures appressed and 

 bordered anteriorly by a strong ridge-like cord or by stronger 

 spirals; the varices are but slightly developed; aperture subellip- 



