GEOLOGY AND PALEONTOLOGY OP THE SCHOHARIE VALLEY 



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f o r m i s [fig. 59], a less oblique species, is also common in this 

 and other horizons. 



The gastropods are well represented by the type Platyceras 

 which is represented by species showing various degrees of non- 

 coiling. P . V e n t r i c o s u m [fig. 60] and P. gebhardi 

 [fig. 61] are the most closely coiled and easily distinguished from 

 each other by the ventricosity of the first species. A few of the 



Fig, 66 Phacops logani 



Fig. 67 Dalmanites 

 pleuroptyx 



more characteristic species with slight coiling are represented in 

 the illustrations [figs. 62-64] and they give an idea of the in- 

 stability of the form of this very variable gastropod. 



Various species of Orthoceras occur in this and in the preceding 

 horizon. They are generally poorly preserved. O. helder- 

 b e r g i a e may be given as an example. 



Among the pteropodous mollusca, C o n u 1 a r i a h u n t i a n a 

 [fig. 65] may be cited. The species is easily recognized by its 

 form and peculiar surface markings. 



Trilobites are not uncommon in this formation, but perfect 

 specimens are not easily obtained. Phacops logani [fig. 66] 

 is one of the most abundant and readily recognized by its strong 



