34 GEOLOGICAL MEMOIRS. 



demonstrative of this explanation ; as things stand at present, we can 

 merely place them separately. 



Prof. Uiiger was the first who recognized theliassic nature of these 

 strata (Wiener Zeitung, 20th of January, 1845; Leonh. u. Bronn's 

 Jahrbuch, 1848, p. 279) ; and M. Kudernatsch has given a detailed 

 geological description of them (Jahrbuch der K. K. Geolog. Reichs- 

 anstalt, 1852, vol. ii. p. 44). 



The time is not yet come to decide about the affinity of these 

 strata with the frequently quoted plant-bearing schists in the western 

 regions of the eastern iVlps, which may perhaps prove to be a connect- 

 ing link between the Gresten and the Koessen strata. 



The reports of the geologists who have surveyed this rather 

 limited district agree in representing the Gresten strata as resting 

 immediately on the Guttenstein strata, — a very unexpected circum- 

 stance, perhaps to be explained by future observations. 



IV. Relation of the Koessen beds with the St. Cassian beds and 



the Lias. 



Having detailed the whole of the facts, and enumerated the 

 fossils, which may induce us to rank this group among the lias, I 

 will briefly discuss the reasons given by some geologists for parallel- 

 izing some of its members with the St. Cassian formation. The 

 whole series of Koessen fossils gives us but three species identical 

 with those of St. Cassian, viz. Cardita crenata^ the so-called Sjjon- 

 dylus obliquus (whose identity seems doubtful even to M. Emmrich), 

 and Actneonina alpina, quoted by M. Merian, but without giving 

 its locality. The Aviculce gri/phce.atcE are found in the lias of 

 England as well as in the St. Cassian strata ; and, according to M. 

 Peters, one of our species may probably prove identical with Avicula 

 contorttty Portl. 



The stratigraphical relations, at least as they exist in Vorarlberg, 

 do not appear to warrant a separation of the Koessen strata from the 

 lias ; what we have already said is sufficient to lead us to the con- 

 clusion that M. Escher's No. 18 limestone with Megalodon tri- 

 queter (the equivalent to our Dachstein limestone) and his No. 14 

 St. Cassian Formation (identical with our Koessen strata) cannot 

 conveniently be considered to be members of different formations. 

 Since the investigation of the Cephalopods of the Salzkammergut, 

 the Hallstatt strata can no longer be doubted to be an equivalent 

 of the St. Cassian formation, nor is there any reason to consider 

 the former as representing only a part of the St. Cassian group. 



No locality is at present known where the Koessen group may 

 not be represented, in one way or in the other, between the Ammo- 

 nitic Upper Lias and the Hallstatt strata. The section referred to 

 by M. Emmrich (Zeitschrift d. Ueutsch. Geolog. Gesellsch. 1852, 

 p. 515) as showing the Adneth strata immediately overlying those 

 of the Hallstatt group, is founded on an error of M. Lippold, who 

 has confounded the last-named group with the Adneth strata. 



Along the whole northern declivity of the eastern Alps the Koessen 

 strata are most distinctly separated from the Hallstatt group by their 



