GEOLOGY AND PALEONTOLOGY OP THE SCHOPIARIE VALLEY 151 



for 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 . ventricosum [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. 67 Dalmanites 



p 1 e n r o p t y x 



Fig. 66 Phacops log ani 



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 mollusea, 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 Hi is formation, but perfect 

 specimens are not easily obtained. P li a c ops 1 o g a n i [fig. 66] 

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



