1912.] 



NATURAL SCIENCES OF PHILADELPHIA. 



375 



lished descriptions and figures necessarily leave much to be desired 

 as far as really complete characterization is concerned. Furthermore, 

 it is generally recognized that because of the relative stability of 

 internal structures as compared with external characters, identifica- 

 tion for purposes of correlation must be based on the latter; indeed, 

 plants may pass from one formation or even period to another with 

 the former apparently unchanged, and of all types of structure that 

 of the araucarias is the most persistent, extending from the Devonian 

 down to the present time. 



It appears, therefore, that there is actually not the slightest 

 foundation for the idea that the deposition of the Newark group 

 began during the Permian or any other portion of the Paleozoic. 

 But it is not by any means certain that more than one limited sub- 

 division of the European Triassic may not be represented within its 

 bounds. 



For purposes of comparison, a table of the subdivisions which have 

 been recognized both here and in Europe is added. 



Table I. Subdivisions of the Triassic. 



13 Lyman, op. cit., p. 197.' and Report on the New Red of Bucks and Mont- 

 gomery Counties, Summo Final Report, Penna. 2d Geol. Surv., Ill, pt. ii, 

 pp. 2589-2638, 1895. Thic nesses somewhat modified in accordance with later 

 work. 



14 Kummel, H. B. The Newark System — Report of Progress, Ann. Rept. 

 State Geol. N. J., 1896, pp. 34-55; thicknesses, p. 59. 



15 Von Huene, F. Eine Zusammenstellung iiber die Englische Trias, etc., 

 Cerdr. Min. Ueol. Raleont., 1908, p. 16; thicknesses from various sources. 



