273 



Chjpeaster, and Spatangus have the typical form of Cidaris. 

 These facts do not look like the effects of sexual derivation, but 

 show a plan, followed in all, and not modified by external circum- 

 stances. We have these animals now, and yet the older forms 

 are not extinguished ; in every generation we see the growth 

 proceed from Cidaris to Spatangus, showing that the laborious 

 growth required by Darwin's theory is not logical. 



Prof. W. B. Rogers made some remarks supplement- 

 ary to those of the preceding meeting, on the effects of 

 a subsiding and a rising ocean-floor, as seen in the strati- 

 graphical relations of the resulting land. 



If we assume an upward movement of the sea-bottom as the 

 leadino- condition under which the paleozoic strata were depos- 

 ited, w"e must admit a depth of the sea at the commencement of 

 these formations so enormous as to be incompatible with the 

 accumulation of the materials of the earlier strata, unless indeed 

 we suppose these strata to have been formed exclusively in 

 positions within a moderate distance of the shore. But this 

 supposition of a comparatively littoral deposit would not explain 

 the conditions in which the strata are actually known to occur. ^ 



We might imagine a series of strata to be successively laid 



down in 1 gentle slope, approximately parallel to that of the 



ancient sea-bottom, each terminating against this surface without 



being continued into the profounder depths beyond, and we might 



supp°ose the floor to be uprising in the region of this accumulation 



at such a rate as to bring successive tracts, farther and farther 



from the ancient shore-line, within limits of depth admitting of 



mechanical and organic deposition. But in such circumstances of 



formation, these earlier strata, instead of extending, as they are 



believed to do, almost continuously over the whole ocean-floor, 



would be seen to terminate at no great distance from the original 



shore-line, by abutting against the bottom at the places where 



the depth had set a limit to their accumulation. 



Thus, therefore, on no hypothesis of a secular rising of the sea- 

 bottom can we explain the formation of our Appalachian paleo- 

 zoic deposits. On the other hand, considering their aggregate 

 thickness, as well as their continuity, composition, and strati- 

 graphical arrangement, we are entided to conclude that they were 



PROCEEDINGS B. S. N. H. — VOL. VII. 18 JUNE I860. 



