Pen-y.] 350 [December 18, 



as we yet know, specifically different. And still, between some of tlie 

 species, there are intimate resemblances. The closeness of this re- 

 lationship is manifestly evident at a glance, on comparing Conoceph- 

 alUes Tfiucer oi' the Georgia Slate with ConocephaUles Adamsi and 

 C. Vutcanus of the Potsdam (to say notlaing of C. arenosus and C. 

 mlnutux, found just beyond the limits of the State) — species which, 

 while distinct, are very closely akin. Should future discoveries indi- 

 cate the existence of several species common to the beds under con- 

 sideration, they will only confirm and strengthen our apprehension of 

 the truth, Avhich we abeady recognize. And so the general, to say 

 no more of a specific or of a generic alliance, is seen to be strikingly 

 intimate, when looked at in a typical point of view, from a wide com- 

 parison of the fossils of the two series of rocks now occupying our 

 attention. 



This being the state of the case, it must seem clear, that Avhile the 

 underlying and the overlying beds are discordant in dip, in strike, and 

 included fossil remains, they are yet nearly related ; that they both 

 should be regarded, when contemplated broadly, as belonging to one 

 and the same great zone of living existence; that the Red Sandstone 

 accordingly claims recognition, and must of good right be recognized, 

 as an upper division of the Taconic, or Primordial System of rocks; 

 nay more, that it follows the inferior groujDS, after a short break in 

 time, and a slight interruption in the organic succession, and seems to 

 cap them with the more mature forms of the same grand type of life. 



V. We may accordingly ask, as a final question, whetlier the Red 

 Sandstone can be jjroperly referred to the Lower Silurian System of 

 rocks ? 



The Potsdam formation has been almost universally counted as the 

 base of the Champlain, or Lower Silurian, beds of New York. And 

 this determination of the mass under examination was very natural, 

 especially at the time and place at which it was originally made; for 

 no fossil-bearing strata were then known to be older; while in Pots- 

 dam, the typical locality, the formation in question rests directly upon 

 rocks usually called igneous. It is moreover succeeded, at many 

 points, by the Calciferous Sandrock, and often by other and later 

 members of the Champlain series. 



It seems to be a fact, however, that the Potsdam Sandstone and the 

 Calciferous Sandrock are stratigraphically unconformable. There is 

 a lack of conformity in dip, in strike, and, as is clear in many cases, 

 in the order of succession.' In other words, we often find evidence 

 that the latter division of rocks did not, at least in all instances, 

 inuuediately follow the former in the order of time. This discordance 

 may be seen in part at Chazy, New York, where the two formations 

 crop out in close proximity, and near their junction, along the western 



