TROPIDOLEPTUS CARINATUS IN CHEMUNG FAUNA 351 



seems to indicate that the marine biotic conditions of the New 

 York Hamilton and the Virginia Chemung seas were more nearly 

 alike than they were in different parts of the same sea in the two 

 states during Hamilton sedimentation. 



A matter of some interest and importance in connection with 

 the recurrence of this species and its associates relates to the 

 location of its Portage habitat, or place of retreat between the 

 close of Hamilton and the beginning of Chemung sedimentation. 

 It has been shown by Prosser 1 and others 2 that in eastern New 

 York the Hamilton fauna including Tropidoleptus carinatus con- 

 tinued in a slightly modified form to live on during Portage time. 

 In other words, this species and some of its allies at the close of 

 Hamilton time became extinct in central and western New York 

 but survived in a narrow belt along the eastern margin of their 

 old habitat and continued to live near the eastern shore of the 

 Appalachian Gulf throughout Genesee and Portage time. (See 

 Fig. 1.) 



In Pennsylvania the writer's work has shown that the Ithaca 

 and Portage faunas bear the same geographic and stratigraphic 

 relations to each other that they do in New York. In western 

 Pennsylvania the Portage formation is characterized by a typical 

 western Portage or Naples fauna. 3 On the Susquehanna River 

 an Ithaca fauna occupies the same horizon which is held by the 

 Portage fauna in the Altoona section. 4 East of the Susquehanna 

 River 35 miles, at Pine Grove, the writer has recently collected a 

 faunule of the Ithaca fauna which shows a more prominent Ham- 

 ilton element than the fauna exhibits at the Susquehanna River. 

 It includes Tropidoleptus carinatus , as will be seen from the follow- 

 ing list of its species : 



1 "The Classification and Distribution of the Hamilton and Chemung Series of 

 Central and Eastern New York," Fifteenth Ann. Rep. State Geol. New York (1897), 

 208-14. 



2 H. S. Williams, "The Correlation of Geological Faunas," Bull. U.S. Geol. 

 Survey No. 210 (1903), 71-72; John M. Clarke, "The Ithaca Fauna of Central New 

 York," Bull. N.Y. State Mus. No. 82 (1905), 53-65. 



3 E. M. Kindle, "Faunas of the Devonian Section near Altoona, Pennsylvania," 

 Jour. Geology, XIV (1906), 633. 



4 H. S. Williams and E. M. Kindle, "Contributions to Devonian Paleontology, 

 1903," Bull. U.S. Geol. Survey No. 244 (1905), 69-92. 



