Clarke — Oneonta, Ithaca and Portage G-roups. 



s] 



(1895), pp. 123-125. The lowest shale beds lie near the base of the Portage 

 group, and are followed by a hand of black shale ("Lower Black band"), 

 forty feet in thickness, above them lying bluish sandy shales with thin flags 

 (95 feet). The latter shales bear fossils at intervals : 



" Ungulina, " mhorbicula/ris. 



Ji uch tola speciosa . 



Product ell a spinulicosta. 



Above these are 125 feet of sandy shales and thin sandstones, which are 

 capped by a western continuation of the red and green nodular limestone or 

 "Goniatite concretionary layer, 71 which is better developed in the Naples 

 valley, and has been frequently described by the writer. 



Thirty -five feet below this concretionary layer the follow ing fossils were 

 found : 



Jfantlcoceras Patersani. 



Bactrites cf. gracilis. 



Belleroph <> n n a tato / \ 



JBuchiold speciosa. 



Lumdicardium ornatu m. 



L. sp. no v., with extremely fine radial striae, frequent in the Naples 

 section. 



Lucvnaf f sp. nov. ; tine lined species representing an undescribed 

 generic form ; abundant in the Naples section. 



At this point, lying just about half-way (twelve miles) between the 

 Seneca lake section on the east and the Naples section on the w est, the true 

 Portage or Naples fauna prevails largely to the exclusion of representatives of 

 the Ithaca fauna. The sections described have clearly shown the gradual 

 appearance' of certain of the more generally diffused species of the Portage 

 fauna (e. g., Ma nti core rax Patersoni, Buchiola speciosa) as far to the eastward as 

 the Tioughnioga valley, in the midst of a highly developed Ithaca fauna ; the 

 diminution of the latter with a notable increase of the former in all Seneca 

 lake stations, and finally a virtual exclusion of the latter, at Branchport, 

 though we do not find here the more prolific development of the former 

 attained in the Naples valley and westward. 



Note.— The diagrams given upon page 62 require a word of explanation. The upper curve in each is not a topographic line, 

 but is employed to facilitate the expression of the varying thickness in the deposits of the Portage epoch. The differential crust 

 movements, which are the important factors in this difference in sedimentation, might also have been suggested by a curvature of 

 the strata underlying the Portage seaiments. There is not sufficient difference in the lithologic character of the deposits through- 

 out their extent to justify an assumption of material diversity in batbymetric conditions. Therefore we regard the Naples region, 

 one of much less rapid crustal depression than the regions east and west. By introducing the upper curve of these diagrams, at 

 the base of the Portage sediments, we might have indicated with approximate accuracy such differential depression of the crust 

 during this later epoch of the Devonian. Such curvatures of the underlying rocks are. however, not vet dcdueible from recorded 

 facts. 



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