FIRST TRACES OF REPTILES. 51 



The total number of specific forms, which had heen dimi- 

 nishing in the carbonigenous era, is in this still further 

 reduced ; one recent author says, from about a thousand to a 

 hundred and sixty-six, of which only eighteen are common 

 to the inferior strata. ( 32 ) It appears as if, while some new 

 species continued to present themselves, the animal kingdom 

 were now generally undergoing a decay, for even specimens of 

 particular families are less abundant than formerly. Instead, 

 for example, of the hundred species of corals of the carbonifer- 

 ous formation, there were now only fifteen, and of these but 

 three or four abundant. Of the numerous crinoidea of the 

 past, but one now remained, and this is rarely found. The 

 trilobite has now vanished, to appear no more. For hundreds 

 of brachiopods, there were now only thirty, ten of them old. 

 The cephalopods almost disappear at the very commencement 

 of the Permian era. 



It cannot at present be determined whether this diminution 

 of fossils is owing to an actual reduction of the amount of life 

 in the ancient seas, or only to some such simple cause as the 

 occurrence of deposits which were not favourable to the pre- 

 servation of animal remains. It may even be that the prin- 

 cipal cemeteries of the age have not yet been hit upon by 

 research ; for certainly this is neither the most extensively 

 nor the most rigidly examined of the various formations, and 

 we are made the more suspicious by finding that, at this part 

 of the rock series, several important fossiliferous strata are 

 present in one region and not in others. It has been ascer- 

 tained, however, by Permian researches, that extensive 

 changes of specific forms in the ancient seas were not, as has 

 been supposed, necessarily and essentially connected with 

 great physical disturbances ; for both do we find that the un- 

 conformability of strata or memorials of disturbance between 

 the carboniferous and Permian do not affect the fossils, 

 and that a conformable succession of strata over the Permian 

 is attended by a great usually called a complete change of 

 species. At this termination of the Permian, modern geolo- 

 gists close what they call the Palaeozoic Period, on a suppo- 

 sit'on that an ancient creation had now passed away, to givo 



B2 



