REPORT OF THE STATE PALEONTOLOGIST 1901 649 



bergian barrier, mentioned above, the region east of the barrier, 

 comprising the Cumberland basin, was steadily going down, the 

 subsidence allowing an invasion of an Atlantic sea and fauna 

 to which the name Helderbergian invasion may be very appro- 

 priately given. 



This invasion brought in a European fauna by way of the 

 Eeroynian oham believed to have connected North America with 

 central Europe (Bohemia, Hartz, etc.). We think this line is 

 in the main correctly drawn by Bertrand, 1 though we would 

 draw it on the American side more to the north — nearer to his 

 Caledonian chain — so as to bring the Helderbergian and Oris- 

 kanian deposits of Gaspe", Quebec, into more direct connection 

 with those of the Appalachian Mediterranean. 



This invasion of the United States began early in Siluric time, Appalachian 



° J 1 Mediterra- 



occupying then and to close of Oriskany time the growing Cum- Cumberland 

 berland basin lying, as described above, east of the Helderberg- 

 ian barrier. The connection between this Appalachian Medi- 

 terranean and the Atlantic, which will be further discussed in 

 treating of the Marcellus invasion and the Skunnemunk trough, 

 is supposed to have been about in the region of Chesapeake bay. 

 To the north and south of Cumberland Md., there is a great 

 series of rocks, beginning with shales and passing upward into 

 limestone, and characterized by a succession of prolific faunas. 2 

 Very few of the species of these faunas are identical with species 

 of the Mississippian sea of Siluric time. The earliest fauna 

 recalls the Clinton, and passes into one which may be compared 

 with the Niagaran, and then a great series of limestones, 

 abounding in minute Ostracoda, which may be compared with 

 the Salina on account of the prevalence here also of larger 

 Ostracoda of the genus Leperditia. Then comes in without 



* ■■ — - — ■■ - — — ___ — ___ — _ — , M , . — — , 



1 Soc. geol. de France. Bui. Ser. 3. 1887. 15:442. 



2 This series of rocks rests on the Tuscarora and Juniata formations. 

 These coarse deposits have afforded very little satisfactory fossil evidence, 

 so that we do not yet know whether they belong to the Mississippian sea 

 or the Appalachian Mediterranean. 



