GEOLOGY AND PALEONTOLOGY OF THE SCHOHARIE VALLEY 221 



ate cardinal line, and rounded to angular umbonal slope, 

 anterior of which there is a faint oblique depression ; Gram- 

 my s i a a 1 v e a t a [fig. 172], a large coarse shell with strongly 

 forward-pointing beak, coarse subregular concentric folds which 

 become obsolete on the posterior portion of the shell ; Pterinea 

 flabellum [fig. 173], an oblique shell with convex left and 



Fig. 179 Spirophyton velum 



flat right valve, large and well defined wing and strong coarse 

 radiating striae increased by repeated intercalations of finer ones. 



Among the commoner gastropods are : Pleuroto m a r i a 

 cap i 1 1 a ]• i a [fig. 174], a strongly sculptured, high spired spe- 

 cies in which the intersections of the lines of growth and the 

 spirals are spinose; P.sulcomarginata [tig. 175], another 

 sculptured form, in which the upper portion of the whorl is flat, 

 so as to produce a conic spire, with the band on (ho outer margin 



