6 GEOLOGICAL MEMOIRS. 



dium, identified by the describer with C. striatulumy Sow., but pro- 

 bably answering to C. Rhceticum, Merian. Wherever molluscous 

 remains are wanting, the widely-spreading and easily recognizable 

 Bone-bed * offers a safe horizon ; and, even if this bed be not discern- 

 ible, the limestones with Ammonites planorhis may be sufficient for 

 obtaining at least an approximative parallelism. Even if the new 

 and imperfectly preserved forms of mollusks occurring in these 

 strata associated with the Bone-bed of Suabia, and provisionally 

 designated as "Junction-beds," be left out of the question, we find 

 contained in them three very characteristic species, which can scarcely 

 be misunderstood : Cardium Rhceticum^ Avicula contorta, and Pecten 

 Valoniensis, none of them having been hitherto found in any horizon 

 much above or below the beds in question. Their appearance in 

 Suabia, near the shores of this ancient sea, in rocks bearing all the 

 characters of littoral deposits, becomes still more interesting by the 

 following considerations. 



The Kossen beds near Vienna, and even considerably farther west- 

 ward, at Kossen, and in the Bavarian Alps, are characterized by an 

 abundance of Brachiopods, by large species of Lima^ by Ostrcea 

 Haidingeri, Gervillia SchafTiaiitli, and G. inflatat while Cardium 

 RhcBticum, C, Austriacum, Pecten Valoniensis^ and Aviculce are 

 but of scarce occurrence in the Brachiopod-limestones, although ex- 

 tremely abundant in isolated layers imbedded in the true " Dachstein 

 Limestonef." 



In the Vorarlberg the Brachiopods evidently become scarce, while the 

 individuals of Plicatula striata, of Cardium, and of the curved forms 

 of Avicida increase in number ; now and then remains of fishes and 

 Bactryllia J, unknown in the Eastern Alps, are mingled with the shells. 



An isolated layer of black slate, with numerous shells of Avicula 

 contorta, Cardium Valoniense, and Gervillia Schafhautli, but without 

 any Brachiopods, is imbedded in the Dachstein limestone of Stallehr, 

 near Bludenz ; whde the Avicula-beds of Salzburg and Tyrol are 

 generally white limestones, containing isolated Brachiopods §. 



We may perceive in the Kossen beds, by following them from east 

 to west, a gradual diminution, and at last a total disappearance, of 

 Brachiopoda and other forms living in deep seas, together with a 

 gradual increase, and finally a prevalence, of other shells almost ex- 

 clusively belonging to the Pectinibranchiata. 



Cassian " and " Upper St. Cassian " (Kossen beds). We are not aware that a 

 single species from the deposits in question occurs at St. Cassian itself. 



* On its extent and constitution, see Quenstedt (Das Flotzgebirge Wirttem- 

 bergs, p. 110) ; Oppel (die Juraformat. Engl. Franckr. u. des siidwestl. Deutschl. 

 1856, pp. 16-24) ; Marcou, " Sur le Jura Salinois " (Mem. de la Soe. Geol. 1848, 

 vol. iii. p. 32) ; Strickland, loc. cit. 



t See Hauer (Jahrbuch der K. K. Geol. Reichsanstalt, 1853, p. 729) ; Suess, 

 " Brachiopoden d. Kossner Schichten " (Vienna Academy Memoirs, vol. vii., and 

 Q. J. G. S. vol. xi. part 2, p. 26). For the present we leave unnoticed the strata 

 of Euzesfeld. 



X These fossils seem here to act the same part as do the small capsules of plants 

 in the older and extensive bone-bed of Ludlow. See Hooker (Quart. Journ. Geol. 

 See. vol. ix. 1853, p. 12) ; and Murchison (Siluria, p. 237, &c.). 



§ See Peters (Jahrbuch der K. K. Geol. Reichsanstalt, loc. cit. p. 185). 



