On the Age of the Sandstones of the Newark Group. 361 
and within the same limits which now appear to result from all 
the subsequent researches. 
At the meeting of this Association held in Cincinnati in April, 
1851, the present writer made a communication on the Post-Per” 
mian character of the red sandstone rocks of Connecticut and 
New Jersey as shown by their fossils. I then exhibited, to- 
gether with two species of Voltzia, some specimens of the genus 
topterus from these rocks, showing the homology of their cau- 
dal structure with that of the Catopterus macrurus from the coal 
rocks of Eastern Virginia. This was induced in part by the 
fact that Sir Philip Egerton, in a paper of Sir Charles Lyell, in 
the Journal of the Geological Society, had separated this Vir- 
ginia species from its congeners in the New Jersey and Connec- 
ticut rocks, on the ground that the former belonged to the homo- 
cercal and the latter to the heterocercal divisions of Prof. Agassiz.* 
Previous however to this publication of Sir Charles, repeated 
and careful examinations, with Prof. Agassiz, of the numerous 
specimens of Catopterus in my possession, collected from the 
localities of the three different States, had appeared to establish 
y their similarity in respect to the structure of the tail. Also 
- Ce mal 
so speak. I therefore reclaim the Dictyopyge of sir Philip Eger- 
ton, founded on my species C. macrurus, as still belonging to the 
instituted by Mr. Redfield for certain ies of heterocercal fish 
ginia fish is stated to be homocercal, and this he my by the 
* Sir Charles Lyell On the Structure and Probable Age of the Coal-Field of the 
— River, Nae Hetchabsae, Virginia: Jour. of the Geol. Soc., vol. iii, 1847, pp, 
5-278, 
SECOND SERIES, VOL. XXII, NO. 66.—NOV., 1866. 
46 
