Maryland Geological Survey 37 



waters having liad their origin in the Arctic and Pacific oceans, wliile the 

 eastern seas were in communication witli tlie Athintie and Gulf of Mexico. 

 To discover tliese connections is the work of paleontologists, a,s the record 

 to he deciphered is mainly contained in the fossils entombed in the strata. 

 The formations of the Apjsalachian region have faunas and species that are 

 often quite like those of Europe, yet at other horizons these are very differ- 

 ent. 1'he Eiiropean connections are more frequently from the northern 

 portion of that continent, but every now and then Mediterranean affinities 

 are discovered. In the former case the faunas traveled back and forth 

 along the Xorth Atlantic shores, while those of the Mediterranean region 

 migrated via Gondwana, a vast transverse land that in the Paleozoic and 

 probably throughout the ]\Iesozoic united India, Madagascar-Africa, and 

 the Brazilian portion of South America. 



An examination of the six paleogeographic maps of Devonian time here 

 presented shows that the Appalachian Sea had two connections with the 

 Atlantic Ocean. In the north, throughout the Lower Devonian, the 

 St. Lawrence Sea opened into the Appalachian trough, and in the former 

 waterway are seen the distinctive northern. European faunas which Clarke 

 has so clearly described.' Many of the species are also found in Maryland, 

 yet the Oriskany faunas of this sea when contrasted with those of the 

 Mississippi Valley are found to be wholly dissimilar. The latter are of 

 South American origin, best known in central Brazil. In the medial 

 Atlantic region there was another opening into the Atlantic during the 

 greater part of the Devonian. On the accompanying maps it is repre- 

 sented as crossing New Jersey, because these deposits, which are of con- 

 siderable thickness and are found in most horizons, are here nearest the 

 ocean. This break into the Atlantic could not have been farther to the 

 north, though it may have occurred more to the south, even as far south 

 as the headwaters of the Chesapeake. Present evidence, however, places 

 it best across New Jersey. Through this opening came many of the 

 Middle and Upper Devonian species described from Maryland, besides a 

 considerable number of the Lower Devonian forms. The Tropidoleptus 

 fauna of the later Devonian for a long time swarmed through New Jersey 



> Memoir 9, N. Y. State Mus., 1908. 



