Gkabau — Faunas of the Hamilton Group. 



323 



creek, a thin bed crowded with Orbiculoidea media occurs seven or eight feet 

 above the base of the Moscow shale. Associated with this species are 

 O. Doria (?), Schizoholu* truncatus, both rare, and a few impressions of Spirifer 

 muoronatus. SchizoLohi* truncatus occurs for the first time in this region, 

 and indicates the approach of the Genesee fauna. 



E. The fauna of the upper Moscow shale, or the Spirifer tullius fauna. 



This fauna occupies the upper four feet of the Moscow shales. The 

 fauna of the upper foot differs from the normal fauna in its more transitional 

 character, and in the absence of S, tulVius. It is therefore separated as a 

 distinct subfauna. 



The normal fauna. 



The most characteristic form of the normal fauna is Spirifer tullius, which 

 has not been found outside of these beds. The specimens are all dwarfed 

 representatives of the larger eastern forms, but otherwise show the characters 

 well. At first the syjecies is rare, or practically absent, but near the middle of 

 the beds it becomes quite abundant. Anibqccelia prammboria makes its first 

 appearance, and is represented by numerous and large specimens ; A. wmbonata 

 has practically disappeared. 



a. At the beginning of this fauna only the following species occur 



(all brachiopoda) : 



77 Schizobolus truncatus. R 



87 Orthothetes arctostriata. r 

 103 Productella spinulicosta. re 

 106 Spirifer tullius. r 



116 Amboccelia unibonata. R 



117 A. prseumbona. c 



b. The normal association of species in the S. tullius tauna is as follows : 



Crustacea : 



1 Phacops rana. r 



Cephalopoda : 



9 Orthoceras subulatum. R 

 Pteropoda : 



13 Tentaculites bellulus. (>) R 



14 T. gracilistrfatus. r 

 Tentaculites sp. it 



