TRANSITION FROM THE PALAEOZOIC NO THE MESOZOIC. 413 



We have given the history of change of opinion in regard to the 

 English section (Fig. 587), because it is a type of many discussions and 

 changes which have occurred and will still occur in geological opinion. 



Area in the United States. — The Permian has been found in the 

 United States, in Kansas, bordering on, and conformable with, the coal 

 of that region (map, p. 287) ; also in New Mexico and Western Texas, 

 and probably also overlying the coal of Illinois (Cope). It gradates so 

 completely into the upper Coal-measures that no attempt has been 

 made to separate them in the map. Until recently nothing of interest 

 has been found in the American Permian, except a few shells (Figs. 

 588-592), but now a considerable number of fishes, amphibians, and 

 reptiles are known. 



An elementary treatise like this must dwell mainly on culminating 

 periods, and their characteristic forms ; and yet to the philosophic stu- 

 dent it is the transitional forms and periods which are the most inter- 

 esting. The Permian is pre-eminently such a transitional period, and 

 contains many transitional forms. In it we have a passing away of 

 Palaeozoic types, a coming in of Mesozoic types, and a coexistence of 

 the two side by side. The change from the one to the other, there- 

 fore, was not sudden and by exterminations and recreations, but gradu- 

 ally by extinction of some old forms and modification of others into 

 new forms ; and all the new forms were thus derived. 



The main features of the Permian life, therefore, were : 1. A lin- 

 gering of coal types of plants, such as the Lepidodendrids and Cala- 

 mites, and many genera of Ferns, but extinction of Sigillarids and 

 increase and advance of Conifers to more varied and modern forms, 

 such as Walchia, Ginkophyllum, etc. (Figs. 593, 594). 2. A lingering 

 of Orthoceratites, square-shouldered Brachiopods, such as Productus 

 and Spirifer, and perhaps of Goniatites, but complete extinction of 

 Trilobites and Eurypterids. 3. A continuance of Ganoids, but under 

 more modern forms (Figs. 595, 596). 4. Amphibians continue in the 

 form of Labyrinthodonts (Stegocephali of Cope), of which some are 

 very modern in form (Fig. 597), but true reptiles are introduced in con- 

 siderable numbers. These first reptiles, as might have been expected, 

 are wonderfully generalized in structure. They connect, on the one 

 hand, with Amphibians, from which they were derived, and, on the other, 

 with the lowest Mammals, to which they gave origin. On account of 

 this connection with Mammals, Cope has called them Theromorphs 

 (beast-like). Thus, then, we have, at this time, Stegocephali, connect- 

 ing Ganoid fish with reptiles, and Theromorphs, connecting Amphib- 

 ians with Mammals. This is shown in the following schedule : 



Theromorphs \ *™£ me Mammals ' 



^gocephali \*£^*™ 



