RAYMOND: CORRELATION OF THE ORDOVICIAN STRATA. 271 



eastern Appalachians and to a small area in western Tennessee and 

 Missouri (Kimmswick of Missouri), and do not occur in the usual 

 Ordovician fauna of the great interior basin. The eastern Appalachian 

 belt extends from Gaspe to Alabama, and includes the "Trenton" at 

 Perce, the Quebec City at Quebec, the "Trenton" of southeastern 

 Quebec, the Chazy and Rysedorph of New York, the Chambersburg 

 of Pennsylvania, the Liberty Hall and Murat of central Virginia, the 

 Holston, Ottosee, Lenoir, and Athens of southwestern Virginia and 

 eastern Tennessee, and the "Trenton" of Alabama. This series 

 includes formations of various ages from Chazy to Upper Trenton. 



Russian genera which in America are restricted to the strata men- 

 tioned above are Sphaerexochus, Lonchodomas, Christiania, Oxo- 

 plecia, and Echinosphaerites. Genera prominent in this group, but 

 only sparingly represented in the interior Ordovician are, Pseudo- 

 sphaerexochus, Remopleurides, and Sphaerocoryphe. 



Of the other genera introduced during Wierland time, Ogygites does 

 not appear in America till late Trenton (Collingwood), Cymbularia is 

 unknown, as are also Cryptocrinites, Cystoblastus, Cyathocystis, 

 Hemicosmites, and Protocrinites. The other genera are more or less 

 common throughout the Middle Ordovician faunas of America. 



Some of the more striking of the Wierland guide fossils are absent 

 from the Chazy, thus preventing what seems otherwise a very satis- 

 factory direct correlation. These are Echinosphaerites, Christiania, 

 and Oxoplecia. The fauna of the Chazy is, in fact, a curious mixture 

 of native and immigrant types. All its large molluscan fauna is 

 probably derived directly from the Beekmantown fauna, and most of 

 its brachiopods are also American in origin. There is certainly nothing 

 in northern Europe like its great profusion of rhynchonelloids, and its 

 Orthidae and Strophomenidae may as well be native types as invaders. 

 Even Camarella, the Chazy representative of the Porambonitidae, is 

 probably of American stock, and does not really represent the Russian 

 Porambonites. In Clitambonites, however, we have a true immigrant, 

 which did very well for a time. 



When we come to the trilobites, however, we begin to see the in- 

 vaders. In the list we notice not only certain native genera, Bathyu- 

 rellus, Isotelus, Isoteloides, Thaleops, and Glaphurus, but also many 

 others, which are actually Russian or derived from Russian stocks. 

 These are, Russiati: — Eoharpes, Lonchodomas, Remopleurides, 

 Nileus, Ceraurus, Pseudosphaerexochus, Nieszkowskia, Sphaero- 

 coryphe, Sphaerexochus, and Pterygometopus; derived from Russian 

 stock: — Cybeloides, Pliomerops, Vogdesia, and Heliomera. 



