ZONE OF HARPOCERAS OPALINUM. 149 



bed at Haresfield and Erocester appears to be the boundary-line between the Lias and 

 Inferior Oolite. In some lists of fossils I observe Am. torulosus entered as a species 

 found at Frocester Hill ; this, in my judgment, is a mistake. Lyt. Mrcinum occurs there, 

 and may have been mistaken for it : I have not yet seen Lyt. torulosum in any English 

 stratum or collection. 



At Blue Wick, near Robin Hood's Bay, Yorkshire, this zone is represented by a 

 band of dark friable shale, in parts micaceous and stained with ferric oxide, and 

 containing Terehratula trilineata, BhyncJwnella ci/nocephala, Trigonia Bamsayi, Belem- 

 nites compressus, and Bel. irregularis. The same species occur in a ferruginous seam of 

 sandstone at Glaizedale, measuring eighteen inches in thickness, so that this bed in the 

 north, as in the midland counties, is only feebly developed. 



Foreign correlations. — The " Opalinus-Thone " was well described by Prof. Quenstedt,^ 

 as it occurs in Swabia, and Am. opalinus. Am. torulosus, Bel. tripartitus, Trigonia navis, 

 Germllia pernoides, Cardium striatulum, Mya angulifera, Nucula Hammeri, and Astarte 

 lurida were enumerated as its leading fossils. 



Dr. OppeP found the beds in Wiirttemberg in the Swabian Alps ; and near Gmiind, 

 Boll, Metzingen, Gomaringen, and Massingen, in Bavaria, in the neighbourhood of Altdorf, 

 and Neumarkt, and in Baden, near Kander. Many of the leading shells figured by Gold- 

 fuss in his ' Petrefacta Germanise ' were collected from this bed at Banz, and near Boll. 



In North Germany this zone has been detected in many localities. Reinecke* first 

 figured Harp, opalinum from a specimen collected near Alten-Banz, Coburg. Rolle* 

 recognised the stratum near Hildesheim, Goslar, and Quedlinburg, and first compared 

 the fossils he collected from these beds with those he had found in strata of the same 

 age in Swabia. Von Strombeck^ discovered the zone near Schoppensted, and Ewald* 

 found the same near Hoym in Saxony. Von Seebach'^ met with this horizon near 

 Wentzen, at the southern margin of Hils, and likewise in a railway-cutting south-east of 

 Greene, from which he obtained a collection of its leading fossils, including Lyt. 

 Mrcinum and Harp, opalinum. Dr. Lepsius^ carefully studied this zone in Lower 

 Elsace, and has given an exhaustive account of the beds in his interesting memoir. I 

 had the pleasure of showing my friend the Frocester Hill section of the Cephalopoda- 

 bed and /Mre«5e-sands, and he at once recognised the marked lithological resemblance 

 they had to their correlative zone in Lower Elsace, upon the study of which he was then 

 engaged. 



1 ' Flbzgebirge Wurtembergs,' pp. 243 and 539, 1843. 



2 ' Juraformation,' p. 308, 1856. 



' ' Maris protogaei Cornu Aram, in Agro Coburgico,' pi. i, fig. 1, 1818. 



* 'Versuch einer Vergl. des Norddeutschen Lias mit dem Scliabischen,' 1853. 



^ ' Thon mit Am. opalinus,' Zeitschr. d. Deut. geol. Gessell., vol. v, p. 102, 1853. 

 ^ ' Schict. des Am. opalinus,' Sitzber. d. Berlin Akad., April, p. 350, 1859. 

 ^ ' Der Hannoversche Jura,' p. 3, 1864. 



* ' Der Juraformation in Unter-EIsass,' p. 4, 1875. 



