1862.] JONES — FOSSIL ESTHERS. 151 



9. Estheria ovata, Lea, sp., is as important in the palaeontology 

 of North America as E. minuta is in Europe ; but its exact geolo- 

 gical place is not denned without difficulty. It has long been re- 

 cognized as an abundant fossil in some of the shales and flagstones 

 accompanying the carbonaceous deposits of South and North Caro- 

 lina, Eastern Virginia, and Pennsylvania ; and its importance has 

 been indicated especially by Prof. W. B. Rogers and Sir C. Lyell. 

 It has passed under the names Posidonomya and Posidonia; and 

 Dr. I. Lea and Prof. E. Emmons have given several names to what 

 at first sight may appear to be distinct forms of this fossil; but, 

 after a careful comparison of specimens, figures, and descriptions, as 

 far as the means at my command allow (and I have been liberally 

 aided by my friends the Brothers Rogers and Mr. C. M. Wheatley, 

 of Phcenixville, Pennsylvania, as well as by Sir C. Lyell), I have 

 come to the conclusion that only one form really exists in these 

 North American Estherian shales, namely, Estheria ovata, Lea, sp. 

 The rarely perfect condition of the valves, owing to the crushing 

 they have usually suffered, and to the imperfect exposure of the 

 edges of the imbedded valves, render it difficult to find trustworthy 

 specimens ; and every one of the forms, figured by Dr. Emmons *, 

 however different from the perfect valve they may appear to be, are, 

 I am sure, only squeezed and imperfect specimens, more or less badly 

 drawn. 



Throughout the wide area in which these Estherian shales occur 

 (500 miles from N. to S.), and at two horizons separated by an 

 estimated thickness of upwards of 2000 feet of strata (on the Deep 

 River), the same species occurs. The only real difference that I have 

 detected in the many specimens I have seen being such modifications 

 of the reticulate sculpture of the interspaces as occurs in other 

 species, and an occasional crowding-together of the ridges into 

 numerous striae, such as we see in Estheria striata, E. concentrica, 

 and others. 



As for the geological age of these Estherian and carbonaceous 

 shales of the Atlantic Slope, we all know that they were formerly 

 grouped as Lower Jurassic (Liassic) by Rogers, Lyell, Bunbury, 

 Marcou, and others ; that Marcou has since argued in favour of 

 their Triassic relationship f; and that Prof. Emmons makes them 

 Triassic in the upper part, and Permian in the lower J; — partly on 



* American Geology, &c. 



f Both on account of certain geognostic features, and Prof. O. Heer's opinion 

 of the Triassic character of some of the fossil plants of Virginia. See Bullet. 

 Soc. Geol. France, 2 e ser. xii. p. 870, &c, and especially ' Geology of North 

 America,' 4to, Zurich, 1858, p. 13 & note, where M. Marcou, after giving an 

 account of various opinions held of the age of the Coal-formation of Eastern 

 Virginia and Carolina, adopts Prof. Emmons's classification of the carbonaceous 

 and Estherian shales of N. and S. Carolina, as being partly Permian and partly 

 Triassic ; both, according to M. Marcou, belonging to one great system, more 

 nearly related to the Secondary than the Primary formations. 



| The occurrence of a Bird's bone in the upper part of the series, and mam- 

 malian jaws {JDromatherium sylvestre) in the lower, as figured and described by 

 Prof. Emmons, and of the tracks of bipeds and quadrupeds in the northern equiva- 

 lents of these deposits, makes this series very interesting to the palaeontologist. 



