PERMIAN ERA. 115 



estuaries in which they held supreme sway, though less 

 localised forms, as palcBoniscus andplatysomus, still occur in 

 abundance ; reptiles of larger growth and curious configura- 

 tion (labyrinthodon) come into view; reptilian and bird-like 

 footsteps (ichnites) can also be traced on the sandstones ; and 

 if American geologists be not mistaken, mammalian life in 

 its lowly marsupial form (dromathermm) now comes for the 

 first time on the stage of being. On the whole, however, 



Jaw of Dromatheriutn silvestre, from the Red Sandstones 

 of North. Carolina (Emmons). 



there seems a paucity of life during the Permian period, when 

 compared with that which preceded it ; and this we may, in 

 the mean time, ascribe partly to geographical changes in the 

 distribution of sea and land, partly to the altered composi- 

 tion of the sea-water in certain areas where we have now 

 magnesian limestones and red ferruginous sandstones, and 

 partly to that change of climate which is indicated by the 

 symptoms of glacial action in the formation of its con- 

 glomerates and bouldery breccias. * 



* Professor Ramsay, who was the first to advocate, in a decided man- 

 ner, the glacial origin of these breccias, founds his belief on the following 

 evidences : 1. The great size of many of the fragments the largest 

 observed weighing (by a rough estimate) from a half to three-quarters 

 of a ton. 2. Their forms. Rounded pebbles are exceedingly rare. 

 They are angular or sub-angular, and have those flattened sides so 

 peculiarly characteristic of many glacier- fragments in existing moraines, 

 and also of many of the stones of the pleistocene drifts, and the moraine 

 matter of the Welsh, Highland, Irish, and Yosges glaciers. 3. Many 

 of them are highly polished, and others are grooved and finely striated, 

 like the stones of existing Alpine glaciers, and like those of the ancient 



