186 Moodie — Distribution of the Fossil Amphibia. 



Art. XYII. — The Migrations and Geographic Distribution 

 of the Fossil Amphibia; by Roy L. Moodie. 



The evidence which is at present available points to the 

 origin of the Amphibia in North America, some time during 

 the late Siluric or early Devonic, possibly within the Devonian 

 entirely. The group is represented as continuing in North 

 America until well along in the Cretaceous, when evidences of 

 the forms are lacking. There can be but little doubt, how- 

 ever, that the Caudata and Salientia existed in North America 

 somewhere in post-Jurassic times, but evidences of their habitat 

 are wanting until the Pliocene and the upper Pleistocene, when 

 they have been reported from Kansas, Arkansas and Texas. 



The Amphibia early migrated from North America across 

 the Atlantic by way of some hypothetical route to Europe, 

 where the group is represented certainly in the Lower Car- 

 boniferous of Gilmerton, Scotland, by Pholidogaster pisci- 

 formis as described by Huxley. The abundant remains in the 

 Upper Carboniferous and Lower Permian of Ireland, England, 

 France, Saxony, Bohemia and surrounding regions, testifies to 

 the vigor of the migrants and their ability to establish them- 

 selves among strange conditions. The environmental condi- 

 tions were, however, similar if not identical to those among 

 which their congeners lived in North America. The problem 

 of the early migration of such slow-moving forms as the 

 Amphibia such vast distances as exist between Illinois, Ohio 

 and Pennsylvania and the western shores of Europe is a diffi- 

 cult one to solve, and so far we know nothing of the paths of 

 migration of these small creatures. It is possible for us to 

 imagine a series of lagoons and swamps extending across the 

 ]Sorth Atlantic land bridge by means of which these animals 

 could, through many eons of time, arrive at the regions in 

 which they have left their remains. 



It has been suggested elsewhere* that the earliest forms 

 might have developed from the same or similar piscian ances- 

 tors, but this seems incredible in view of the close relation- 

 ship existing between the Branchiosauria of Saxony and those 

 of the Mazon Creek beds where the genera are closely related 

 and all belong to the family Branchiosauridse. It is a matter 

 of great interest that the Amphibia developed along parallel 

 lines in Europe, Asia and North America throughout all post- 

 Paleozoic time. The same orders, with the exception of the 

 Apoda, occur in the various continents. 



* Journ. Gool., xvii, p. 39, 1909. 



