THE TULLY FAUNA 957 



4:. Stropheodonta per plana var. tulliensis H. S. Williams. 



This, according to Williams, is a derivative of 8. perplana of the Ham- 

 ilton, leading from that to 8. mucronata of the Ithaca. 



5. Platyceras symmetricum var. 



A modification of the Hamilton form. 



(3) The most significant of the immigrant species into this fauna are 

 the following: 



1. 8chizophoria tulliensis (Vanuxem). 



This is clearly an emigrant from the lowan and Michigan Traverse 

 fauna, where its ancestors are found. 



2. Hypothyris venustula Hall. 



This species, commonly made a varietal form of the European H. cu- 

 boides (Sowerby), is the most characteristic of the immigrant forms. As 

 shown by Prosser, it was one of the first to come, while the Hamilton 

 fauna was still in its purity and just before the building of the Sherburne 

 Bar. In the Traverse (Wapsipinicon) of Iowa occurs the closely related 

 H. intermedia Barris, which, according to Walcott, is identical with the 

 H. emmonsi (Hall and Whitf.) of Nevada. It is there associated with 

 Gypidula comis. I have elsewhere^ shown that the Wapsipinicon of Iowa 

 is essentially Lower Traverse, exclusive of the Independence shale, which 

 may be pre-Traverse or Dundee in age. In western Europe the species 

 associated with Hypotliyris cuhoides are either forms which for the first 

 time have representatives in our Chemung faunas or are types which are 

 found in the lowan and western Michigan Traverse. Among the latter 

 are Pugnax pugnus (Mart.), Pentamerus {Gypidula) galeatu^ (Dalm.), 

 Schizophoria striatula (Sloth.), 8pirifer verneuili Murch., Atrypa con- 

 centrica, Cyathophyllum hexagonum, Prismatophyllum pentagona, E. & 

 H., P. goldfussi, Phillipsastrcea (Billing sastrcea) verneuili E. & H., 

 Favosites cervicornis, and others. The fauna of the Mackenzie Eiver re- 

 gion also shows close afiinity with the Cuhoides fauna of Europe, and the 

 connection with west Europe may be traced through Asia, where H. cu- 

 hoides has been found in China and Persia and in the Urals, Petschora 

 land, and Poland in eastern Europe. 



It is thus evident that, as pointed out by J. M. Clarke, the pathway 

 between Europe and America along which the dispersal of H. cuhoides 



» Report on the Traverse group submitted to the Michigan Geological Survey ; not yet 

 published. 



