294 



Report of the State Geologist. 



rare. Associated with it in almost every case are Chonetes lepida and 

 C. scitula. Pliacops rana also occurs plentifully dispersed throughout nearly 

 all the beds. This fauna I shall call the Spirifer miwronatus fauna. Its 

 range is coextensive with the Lower shales, being limited below by the 

 Strophalosia bed, and above by the Encrinal limestone. 



The following are its subdivisions in the region under discussion : 

 a. The Lower Pleurodictyum or Nautilus bed. 



This is a bed of calcareous concretionary masses, embedded in shale, the 

 whole resting upon the Strophalosia bed. Nautilus magister Hall, is the most 

 important fossil in this bed, this being the source of the type specimens. So 

 far as I have been able to ascertain, this species is not found outside of this 

 bed, and it therefore belongs to the lowest bed of the Hamilton stage in this 

 section. The most abundant fossil and the one characterizing this bed 

 in all its outcrops, is Amboccelia umhonata var. nana, and with the 

 exception of the three specimens recorded from the Strophalosia bed (which, 

 as stated above, differ from the type forms), this variety does not occur 

 elsewhere in the Hamilton beds of this region. Associated with it and 

 equally abundant, is Camarotoechia Dotis and it, too, is practically restricted 

 to this bed, the few specimens recorded from other beds differing from 

 these in their general appearance. These two species occupy the rock in 

 places to the exclusion of nearly every other form. In this bed Pleurodictyum 

 styl&pora also makes it first appearance, the specimens, however, not being 

 very numerous. The complete list of fossils obtained from this horizon is as 

 follows : 



Crustacea : 



3 Homalonotus Dekayi. r 



Cephalopoda : 



8 Nautilus magister. c 



Pteropoda : 



17 Coleolus tenuicinctus. r 



Gasteropoda : 



24 Platyostoma (Diaphorostoma) lineata. r 

 29 Pleurotomaria Itys (and variety), re 

 33 Bellerophon Leda. r 



