GEOLOGY AND PALEONTOLOGY OF THE SCHOHARIE VALLEY 199 



Fig. 132 Pentagon ia unisulcata 



[fig. 132], easily recognized by its peculiar form; A try pa 

 reticularis [fig. 133], generally quite robust; and Pen- 

 tamerella a rat a [fig. 100], a pentameroid shell with 

 strongly arching beak as in Gypidula, but with sinus in the 

 pedicle valve and cor- 

 responding fold in the 

 brachial valve, though 

 these are not always 

 pronounced. Strong 

 bifurcating rounded 

 plications cover all ex- 

 cept the upper part of 

 the beak. Finally 

 among the more com- 

 mon species should 

 be named Amplii- 



g e n i a e 1 o n g a t a [fig. 131] , which when full 

 large, terebratuloid shell not unlike Rensselaeria but proportion- 

 ally w r ider. The internal characters are pentameroid and the sur- 

 face is covered with fine 

 radiating striae. 



Among the gastropods 

 the following are com- 

 mon and characteristic : 

 Plat veer as dumo- 

 sum [fig. 135], an 

 extremely spinose shell, 

 with the apex enrolled. 

 The form varies from sub- 

 cylindric in the adult to extremely ventricose. Diaphoros- 

 toma line a turn [fig. 136], a close coiled, nonumbilicate, 

 low-spired shell, with uniformly enlarging suborbicular aperture, 

 and fine spiral striae cancellated by the lines of growth. 

 Euomphalus decewi [fig. 137], a flat coiled shell with 

 the whorls enrolled in nearly the same plane and barely touch- 

 ing, and with a strong carina on the upper part of the last whorl, 



Fig. 133 Atrypa reticularis 



