Cope ([105]), in 1865, began his researches among the Coal Measures Amphibia of North America by the description of Amphibamus grandiceps from the Mazon Creek shales of Illinois. Ten years later ([123]) he published a complete synopsis of the Carboniferous Amphibia of North America, with especial reference to the Linton, Ohio, species, illustrating many of the forms now known from Linton. Between the years 1865 and 1897, Cope published numerous papers ([105-177]) on the Amphibia of the Paleozoic, and to his researches is due a large part of our knowledge of these forms.
Great credit is due Dr. J. S. Newberry ([495], [498]) for the enthusiasm and interest which his collections of Coal Measures Amphibia exhibit. He furnished Cope with the majority of the type material described by him, and it was through Dr. Newberry's instrumentality that the "Synopsis of the Extinct Batrachia from the Coal Measures" ([123]) was published. The material which Dr. Newberry had collected he took with him from Ohio to Columbia University, New York, and a part of his collection still remains in the geological collection of that institution, although the greater portion has been transferred to the American Museum of Natural History. The Newberry collection forms the basis for the larger part of this memoir.
Between the year 1853 and the early nineties, Dawson continued ([200-223]) his researches on the Amphibia of the Coal Measures of Nova Scotia. His most notable single work ([208]) is "The Air-Breathers of the Coal Period," published in Montreal in 1863, in which he gives a complete account of the forms then known from Canada, attempting some restorations. Since his death there have been no new species described from Canada, and, so far as I can learn, there has been no further collecting at the South Joggins.
Recently G. F. Matthew ([409]) has rearranged the classification of amphibian footprints from Nova Scotia. Jaekel ([347]) has described very fully the remains of Diceratosaurus punctolineatus (Cope) from Linton, Ohio, basing the new genus on a species described by Cope as a member of Ceraterpeton. Hay ([316]) has added to the knowledge of the anatomy of Amphibamus, his most interesting contribution being the detection of long, curved ribs in this form. This character excludes the species from the order Branchiosauria and shows the relationship of the form to the Hylonomidæ and the Microsauria. Schwarz ([540]) has described the characters of the vertebræ and ribs of several genera of the Coal Measures Amphibia and has ([541]) offered his views as to the descent of the Amphibia, based entirely on his work on the vertebræ of species from North America and Europe.
Since 1908 the writer has published several contributions ([457-489]) on the Amphibia from the Coal Measures of North America. The results of these investigations are given in this work.
[CHAPTER III.]
STRATIGRAPHIC AND GEOGRAPHIC DISTRIBUTION OF AMPHIBIA IN THE COAL MEASURES OF NORTH AMERICA.
There are but four localities in North America which have furnished any notable remains of Amphibia in the Coal Measures. These are, in the order of their discovery, the deposits at the South Joggins, Nova Scotia; the Linton, Ohio, Coal Measures; the Mazon Creek, Illinois, shales; and the Cannelton slates near Cannelton, Pennsylvania. There are, however, several other localities on the continent which have furnished evidences of Amphibia in the Coal Measures. The principal one of the latter localities is doubtfully of Coal Measures age, although recent discoveries would tend to show it is such. The deposits in question, those of the Clepsydrops shales of Vermilion County, Illinois, have, heretofore, been regarded as Permian, but the discovery of similar remains in rocks of undoubted Pennsylvanian age in Pennsylvania would seem to indicate that the Illinois deposits were contemporaneous with them.