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 

 Catopterus from these rocks, showing the homology of their cau- 

 dal structure with that of the Catopterus rnacrurus 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 

 fully their similarity in respect to the structure of the tail. Also, 

 that the Catopteri of all the localities, including Virginia, might 

 continue to be referred to the homocerci, as in the case of several 

 European genera, or that, mpre properly both they and the other 

 fishes of these rocks might be referred to a distinct and interme- 

 diate division, which is sw6-heterocercal in its character, if I may 

 so speak. I therefore reclaim the Dictyopyge of sir Philip Eger- 

 ton, founded on my species C. macrurus, as still belonging to the 

 genus Catopterus. I refer to this matter on the present occasion 

 on account of the important bearing which it has on the geologi- 

 cal age of these fishes, as found in the several states. 



It may be added in further explanation, that Sir Charles Lyell 

 in the paper referred to, states that " the genus Catopterus was 

 instituted by Mr. Kedfield for certain species of heterocercal fish 

 from the Connecticut red sandstone." He seems not to have 

 noticed that the genus was instituted by Mr. J. H. Kedfield in 

 1836 for a homocercal fish, according to the characteristics afforded 

 in the Poissons Fossiles of Agassiz ; and he probably alluded only 

 to my own later notices in this Journal, 1811, vol. xli, p. 27. 

 All the fishes obtained by him from the sandstone of the Con- 

 necticut river are also pronounced heterocercal, while the Vir- 

 ginia fish is stated to be homocercal, and this he supports by the 

 opinions of Prof. Agassiz as given on first seeing his specimens 



* Sir Charles Lyell On the Structure and Probable Age of the Coal-Field of the 

 James River, near Richmond, Virginia: Jour, of the Geol. Soc., vol. iii, 1847, pp. 

 275-278. 



SECOND SERIES, VOL. XXII, NO. 66.— NOV., 1856. 

 46 



