GENERAL OBSERVATIONS. 



373 



margins. The fingers in the Proterosaurus call to mind those of the Pterodactyl, as 

 The name Proterosaurus is from n-porepos, first, and o-aOpos, lizard. 



Fig. 697. 



Geinitz suggests. 



as Orihis. 



Proterosaurus Speneri. 



Various footprints of Reptilians and Labyrinthodonts have been 

 found in the Permian of Germany; among the latter, Saurichnites 

 salamandroides Gein., and among the former, S. lacertoides Gein., 

 feet with arcuate finger-impressions. Copivlites, or fossil excrements, 

 of Reptiles or Fishes, have been found near Zwickau and Mansfeld. 



The Paleozoic character of the life of the Permian, as already 

 shown, is strongly marked. Geinitz observes, further, that the Tere- 

 bratula tlongata Schlot. of the Zechstein approaches a Devonian 

 form ; Camarophoma Schlotheimi Kg. (Zechstein) is near the Car- 

 boniferous C. crumena Mart. ; Spirifer Clannyanus Dav. (Zechstein), 

 the Carboniferous S. Urii; Spiriferina ci-istata, the Carboniferous 

 S. octoplicata. The genus Schizodus ends with the Permian, as well 

 Camarophoria, Productus, and Strophalosia. 



IV. GENERAL OBSERVATIONS ON THE PALEOZOIC AGES- 



I. Rocks. 



1. Maximum thickness. — The maximum thickness of the Silurian 

 rocks of North America is at least 25,000 feet ; of the Devonian, 

 about 14,400 feet; and of the Carboniferous, nearly 16,000 feet. 



2, Diversities of the different Regions of the continent with regard 

 to the kinds of rocks. — The rocks of the Appalachian region are 

 mainly fragmental, the limestones forming only a fourth of the whole 

 thickness. The strata of the Interior Continental basin are mostly 

 limestones, these constituting full two-thirds of the series. Although 

 New York is situated mostly within the Interior basin, it still adjoins 

 the Appalachian region, and partly lies within its border. Some idea 



