ESTHERTA OVATA. "85 



For most of these illustrations^ we have had recoiirse to specimens from Pennsylvania, 

 Richmond, and Dan River (from Prof. W. B. Rogers' collection), which evidently belong 

 to the same species. These specimens are — 



1 . Erom Pennsylvania. Black shale. EstliericB excessively crowded in horizontal layers. 



2. From Prince Edward, near Richmond, Virginia. Black shale, with conchoidal 



fracture, fine-grained. Estherice tolerably well preserved, but crumpled. 



3. From Dan River, North Carolina. Black, laminated shale, obliquely crushed. 



Estherice very thin. 



Another specimen (from which figs. 28 — 30 have been taken) is a hard, dark-grey, 

 stony shale, containing a few scattered Estheria and a fragment of Eqidsetites, brought 

 from Hardin's pit, Richmond, Virginia, by Sir C. Lyell. 



As in India so in North America there are fossiliferous and coal-bearing shales and 

 sandstones, the geological age of which is far from being exactly known ; these are the 

 plant-bearing beds of Eastern Virginia and North Carolina, with the Estherian shales of 

 the same States and of Pennsylvania, usually known as the Middle and Lower Secondary, 

 or Lower Mesozoic, coal and sandstones of the Atlantic slope. I propose to refer these 

 interesting: strata to the Bhaetic formation while treatino- of their fossil Estherice. 



In 1843, Prof. W. B. Rogers discovered in Prince Edward County, Virginia, a 

 little fossil which he referred to the European Posidonomya mimita ('Proceed. Acad. 

 Nat. Science, Philadelphia,' vol. i, p. 249); and in 1854 ('Proceed. Boston Soc. Nat. 

 Hist.,' 1856, vol. V, p. 14)^ in treating of the close relationship of the several tracts of the 

 " Middle Secondary Rocks " of North Caroluia, Virginia, Pennsylvania, and Massachu- 

 setts, and of their probable Jurassic age, he again alluded to this little fossil, but pointed 

 out that both it and another form associated with it " differ in proportion from the 

 P. minuta of the European Trias." According to Prof. W. B. Rogers, the " Posidoniae " of 

 North Carolina (Dan River) "were noticed as early as 1839, by Dr. G. W. Boyd, while 

 on the Virginia Geological Survey," 'Proc. Boston Soc. N. H.,' vol. v, p. 16. 



In 1847, Sir. C. Lyell described and figured two apparently Avell-conditioned Estheria 

 from the Mesozoic coal-shale of Richmond, Virginia, ' Quart. Jouru. Geol. Soc.,' vol. iii, 

 p. 274 (fig. 6) ; but unfortunately the specimens cannot now be found.^ The woodcut, 

 though good, does not fui-nish sufficiently exact evidence of the superficial sculpturing of 

 the shell to enable me to compare it satisfactorily with my own material, though fig. 28 

 supplies its place to some extent. In this paper Sir C. Lyell stated (p. 275) that he 

 shared Mr. Morris's doubts as to whether the " Posidonomyse " from Richmond, as well 



^ Since these illustrations were drawn and the accompanying text placed in the printer's hands, I 

 have received through Mr. C. Wheatley's liberal kindness a large collection of the Estherian and Cypri- 

 uiferous shales from Plioenixville ; and some notes x)n these will be appended in the sequel. 



2 These Estheria: are also figured in Lyell's 'Manual of Geology,' 5th edit., p. 332, fig. 422, a, h. 



