!> FOSSIL ESTHERLE. 



In both of the foregoing extracts this red sandstone is treated of as Triassic in age ; l 

 but of late years it has been referred to the Permian formation, as shown by the Pal. 

 catopterus being termed " Permian " by Sir P. Egerton in the ' Quart. Jour. Geol. Soc./ 

 vol. vi, p. 9, and by Mr. Morris in his ' Catalogue of British Fossils,' 2nd edit., 1854, 

 p. 336. Its geological place has not yet been determined by the geological surveyors, 

 and for the present I prefer to regard it as of Permian age. 



The stratigraphical position of the red marl and sandstone of Rhone Hill (Tyrone) is 

 noticed at p. 481 of Portlock's 'Report Geol. Londonderry,' &c. The red marl is re- 

 garded as the same as that underlying the Chalk and Greensand at Benbradagh (London- 

 derry), and having a thickness there of between 600 and 700 feet, and overlying marls 

 and sandstones, not less than 1000 feet thick, to which succeed the Carboniferous and 

 Devonian strata. 



6. Estheria minuta, Alberti, sp. PL I, figs. 28—30 ; PL II, figs. 1—7 ; PL V, figs. 8, 9. 



Posidonia minuta, Alberti. Von Dechens De la Beche's Handbuch der Geologie, 1832, 

 p. 453. 



— Goldfussii, Alberti (?). Ibid. 



— Keupertana [vel Keuperina], Voltz. Ibid. 



— minuta (Goldfuss), Alberti. Jabrbuch f. Min., 1832, p. 227. 



— — (Alberti), Zieten. Die Versteinerungen Wurttembergs, 1833, p. 72, 



pi. 54, fig. 5. 



— — (Goldfuss), Alberti. Monograpbie, &c, 1834, pp. 114, 120, 121, 202. 



— — Goldfuss. Petrefact. Germanise, pars ii, 1834-40, p. 118, pi. 113, fig. 5. 



— — Voltz. Mem. Mus. Nat. Hist. Strasbourg, 1837, vol. ii, p. /. 



— Albertii, Voltz. Ibid. 



Posidonomya minuta, Bronn. Letb. Geogn. (1835-38), vol. i, p. 1G4, pi. 11, fig. 22. 



— — Strickland and Murchison. Transact. Geol. Soc, 1840, 2d ser., 



vol. v, p. 337, pi. 28, fig 4. 



— — Bronn. Letb. Geogn., 3rd edit. (1851), vol. ii, part 3, p. CO, pi. 



11, lig. 22. 

 Estheria minuta, Rupert Jones. Quart. Journ. Geol. Soc., vol. xii, p. 37(3. 



„ c. , . (Height of valve... -]4 inch") _, 



l'rom Sinsheim < , r > Proportion 1G to 21, or 1 : U — 



(^Length || „ ) 



(Height 



(.Length 



12. 

 12 » 



Height, more than § 



Length I 



From Sulzbad, var. (Height, less than J ff „ 



Proportion 18 to 27, or 1 : li. 

 Proportion 1 to 1 1 . 



om Sulzbad, var. (Height, less than J- „ ) 

 in .■■ i . > Proportion 7 to 12, or 1 : 14 — 



Albevtu (Length }, „ ) 



1 We must remember, however, that each of the terms "New Red Sandstone" and "Poikolitic" 

 comprised, until about 1841, both the "Upper Red Sandstone" and the " Lower Red Sandstone," the 

 latter of which was then divided oil', with the magnesian limestone, under Murchison's term "Permian." 



