450 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



ditions, quite independent of crust-movements*. James Hall (Sill. 

 Journ.n.s.xxiii.p. 194), in some degree confirming this opinion, says, 

 " It would appear that at a period long preceding the commencement 

 of the Carboniferous-limestone deposits, the ancient ocean began to 

 contract its area :" and then (p. 195) makes the following remark- 

 able statement — that " The coal-measures [of the Mississipi Valley] 

 extend much further to the north than the northern limits of the Car- 

 boniferous limestones, and are spread out over the thinning and 

 slightly inclined edges of these beds, and over the more disturbed and 

 highly elevated edges of the rocks of the preceding periods ; so that 

 the coal-measures rest respectively upon all the formations from 

 Lower Silurian to the Carboniferous Limestones." 



By these observations it is intended to show that probably the 

 strata of this basin near the Mississipi gradually died out, and were 

 not much disturbed : but at present so little is known of the geological 

 structure of the Western States that, no general conclusions can as 

 yet be safely drawn. 



Palceont'ological Break. — The pal&eontological break, according to 

 the Professors Rogers, is " more remarkable than the physical," 

 only three dilapidated fossils with a few indistinct fragments having 

 escaped the general wreck f- 



But the non-transmission of animal or vegetable life into the 

 upper strata is by no means the unerring indication of a break of 

 stage — much less of system, — or of any extraordinary and radical 

 discontinuance of action ; were it so, we should be afflicted with a 

 chaotic multiplication of stages in palaeozoic times. 



Potsdam Sandstone neither receives nor transmits life. Calciferous 

 Sandstone transmits only one species upwards. Medina Sandstone 

 only one {Orthoceras multiseptum) ; Chazy Limestone, five ; Birds- 

 eye Limestone, four ; while from other Silurian strata many forms 

 of life pass upwards. 



In the same way, in the Devonian system, Onondaga Limestone 

 transmits doubtfully a single brachiopod (Atrypa reticularis) ; Mar- 

 cellus Shale, only four ; Portage group, two ; and the Chemung, 

 none whatever. From Oriskany Sandstone seven fossils escape up- 

 wards ; and from Corniferous Limestone and the Hamilton section, 

 thirteen each. 



The palaeozoic law of life is, that the vast majority of every 

 epochal fauna, if not the whole, live and perish together. Agassiz| 

 insists upon the existence of this law with very great rigour — with a 

 rigour which is excessive, according to our present knowledge. 



This great naturalist says, " As fossil remains are studied more 



* From Niagara to the Mississipi, about .... 690 miles. 

 „ middle of Appalachian chain to Cincinnati 320 „ 

 „ New York to River Mississipi .... 950 „ 

 ,, Albany to Utica 120 „ 



f Professor Hall states that he is in possession of other fossils, but so broken 

 up and abraded that they are indeterminable. 



J Contributions to American Natural History, vol. i. pp. 96, 104. 



