NW. Ford—Primordial fossils of Rensselaer Co., N.Y. 9211 
includes all the time from near the beginning of the melting of the 
glacier, down to that in which these old alluvial or Champlain 
deposits became terraced in consequence of a general rising of 
the land, when what I have called the Terrace or Recent epoch 
began. _ According to my view, the terraces are not a result of 
depositions in the Terrace era, (as is represented in the Vermont 
Geological Report (4to, 1861)); they are due simply to the 
below the present level, for the Champlain era, and an upward 
again for the Terrace era, with the change in each case great- 
est to the north—that is, to a limit north yet undetermined. But 
such a general system of changes does not preclude the occur- 
rence of minor oscillations up or down, in different regions dur- 
ing each of these eras, or imply that such changes may not be 
now in progress, 
Nore To pace 204.—The fact that the glacier in the St. Law- 
B 
have been made at any time by a movement down stream, unless, 
Owing to an unequal rate of melting (in the opening of the Cham- 
Art. XXTV.—On some new species of Fossils from the Primordial 
or Potsdam group of Rensselaer county, N.Y. (Lower Potsdam); 
by S. W. Forp. 
Archeocyathus? Rensselaericus, 8p. OV. 
THE only specimen clearly belonging to this species that has 
come under my notice is exceedingly small, being only 0°30 of 
by Mather and the Lower Silurian of New York; but not 
by Vanuxem or Hall. Prof. Hall, in his works, has, like most others, employed the 
name Lower Silurian in As there is nothing in my view to be a ae 
restoring to the Lower Silurian the term Champlain, and no likelihood that 1 
ever be so restored, this term is here retained for a division of the Post-tertiary or 
Emmons for the whole of 
Am. Jour. So1.—Turp Sznizs, Vou. V, No 27.—Maxcz, 1873. 
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