INTRODUCTION 



The Devonian is represented along the Western Valley of 

 Tennessee by highly fossiliferous formations of Helderbergian, 

 Oriskanian, and Onondagan age. Unconformably overlying 

 these strata is the widespread but nearly unfossiliferous Chatta- 

 nooga shale, which is referred with some question to the late 

 Devonian, but which may be of early Mississippian age. The 

 stratigraphy and correlation of these Devonian formations have 

 recently been discussed by the writer elsewhere.^ During the 

 study of the faunas it was found that a number of characteristic 

 indigenous forms are new to science, and these it is the purpose 

 of the present paper to describe. There are thirty-seven new 

 species, and three new genera. 



The accompanying synoptic table (page 114) will indicate the 

 sequence and something of the character of the several Devo- 

 nian formations. The Linden or Helderbergian group is here 

 well developed, consisting mostly of limestone and calcareous 

 shale, with a thickness of about 250 feet. Three breaks in this 

 sequence separate the Helderbergian of Tennessee into four 

 formations, but one finds it difficult to correlate these divisions 

 in detail with the four divisions of the same group in the Appa- 

 lachian trough. The reason for this is to be found in the fact 

 that the Devonian of western Tennessee belongs to a southern or 

 Gulf embayment. This epeiric sea was for the most part iso- 

 lated and measurably independent of the Appalachian trough. 

 In general, the Helderbergian seas were rather restricted in their 

 spread except during the New Scotland epoch, when in many 

 countries there was an expansion of the seas. At this time only, 

 during the Helderbergian, is there clear evidence of direct com- 

 munication between the Appalachian trough and the southern 

 embayment which was covering western Tennessee ; and the 

 Birdsong shale fauna is then so nearly identical with that of the 

 New Scotland of New York as to show not only exact equiva- 

 lence in age, but also direct faunal inter-dispersions. Even at 



^ Stratigraphy and correlation of the Devonian of western Tennessee. 

 Amer. Jour. Sci. (4), vol. 46, 1918, pp. 732-756. Published in more 

 extended form as Bulletin 21 of the Tennessee Geological Survey, 1919. 



