FAUNAL CHARACTERISTICS OF THE SEDIMENTS 355 



and Platyscliisma helicites (Sowerby). The Ostracoda and Leperditia 

 are also of frequent occurrence and often in great abundance in this 

 upper member. 



These characteristics of the generic association, the progressive change, 

 and the identity of certain species in the faunas are illustrated by the 

 passage from the Upper Ludlow into the Temeside groups of the typical 

 section in England described by Elles and Slater/^ but are not repre- 

 sented by any other series of beds on the American continent, so far as I 

 am at present aware. 



Formation V is distinguished from the lower formations by the entire 

 absence of Brachiopods except the genus Lingula and the great abun- 

 dance of a small Pelecypod we have previously listed as Modiomorpha cf. 

 subalata, which on further study appears to represent Anodontopsis 

 augustifrons McCoy. The formation is tied to the next lower formation 

 by the continuance in great abundance in some beds of the Leper ditias 

 and Ostracoda. Distinct traces of Pterygotus problematicus Agassiz 

 'are also found in this formation. 



This combination of characters recalls the terminal Silurian beds of 

 Great Britain called Downtonian and Temeside rather than anything 

 expressed on the interior of the American continent. 



Formation VI is the Perry formation, the fossil plants of which have 

 already been described by Mr, David White,^^ who has confirmed Daw- 

 son's correlation of it with the Devonian. This formation lies uncon- 

 formabl}^ on the beds of formation V. 



The above statements will suffice to indicate the facts of general inter- 

 est which the detailed study of the Eastport faunas is bringing to light. 

 The description of the species is in progress, many new species are being 

 discovered and illustrated, and it would be premature to make any 

 announcement regarding them at the present time. When the faunas 

 are fully elaborated I hope to be able to establish the relationship exist- 

 ing between the Eastport faunas and the terminal portion of the Arisaig, 

 the Silurian faunas of Penobscot Bay, and the Ashland faunas of Aroos- 

 took County, Maine. The facts. already brought to light, however, make 

 it clear that the series of beds here referred to as formations III, IV, 

 and V have a more intimate relationship to the series of formations of 



^ Highest Silurian of the Ludlow district of England. Quarterly Journal of the Geo- 

 logical Society, vol. Ixii, 1906, p. 219. 



'1 G. O, Smith and David White : The geology of the Perry Basin of southeastern 

 Maine. U. S. Geological Survey, Professional Paper No. 35, 1905. 



