SUESS KOSSEN BRACHIOPODA. 31 



although very different in petrographical character, are connected with 

 each other by their fossils ; their peculiar faunas being but special 

 modifications of the richer one in the Koessen strata, which embraces 

 nearly all the species of the others. Two abnormal members, viz. 

 the Dachstein limestone and the strata W\ih.Rhynchonella pedata, are 

 connected stratigraphically with the above-mentioned palseontologi- 

 cally united group. The peculiar stratigraphical relations produced 

 by the intimate connexion of all these subdivisions must be carefully 

 examined. If e. g. the black Koessen strata be said to be a for- 

 mation extending from the Brandner Ferner to Gumpoltskirchen, this 

 assertion does not imply that all the points belong really to one and the 

 same line. M. Peters mentions these beds as occurring near Unken 

 and Lofer between two limestones, both of which ought to be placed 

 with the Dachstein limestone ; nor is this surprising after what is 

 known concerning the fauna of the Starhemberg strata ; the farther 

 solution of these questions must be left to geological investigations 

 of the localities. 



The whole series of these strata lies upon the Hallstatt strata, which 

 contain the fossils of St. Cassian and belong to the Upper Mus- 

 chelkalk ; it is covered by strata containing, in some rare cases, 

 fossils of the upper lias, and having so few species identical with 

 those of the immediately overlying strata, and generally so different 

 from them by the appearance of a rich fauna of Cephalopods and 

 Gasteropods, that we are warranted in considering them as the supe- 

 rior portions of the lias formation. Nor is there any doubt of the 

 age of this group of strata, with respect to their stratigraphical relation. 

 If we indeed admit this group, in which the Dachstein limestone 

 alone has frequently a thickness of several thousand feet, to be an 

 equivalent of the lower lias, we must own that such a development 

 of a subordinate division in the secondary rocks is scarcely to be 

 met with in any other country. 



This vast development of single members must be the cause of a 

 great many peculiarities. Wherever the Dachstein limestone appears 

 in such force, the lower strata bear no traces of organic life. The 

 levelling influence of such an enormous deposit, and the decrease of 

 the water- depth depending on it, is evidenced by the appearance of 

 fossils at only some thousand feet above the lowest limit of the 

 Dachstein limestone, e. g. in the Echern Thai. The strata with Rhyn- 

 chonella pedata may have corresponded to a rather low horizon. 



A consideration of the limits of the contemporaneous seas, as de- 

 termined by the orographic relations existing at this remote epoch, 

 may be useful for the better comprehension of these facts, taken in 

 their totality. A number of geological maps, e. g. the littoral 

 map of the Jurassic Seas, published by Gressly, exhibit the con- 

 tinent of the Schwarzwald and the Vosges, and to the south-westward 

 the central table-land of France, as rising above the level of the 

 liassic deposits. Notwithstanding, we still have no proof of these 

 waters having covered the whole of eastern or south-eastern Switzer- 

 land. 



M. Studer says, " We enter a new region on the opposite bank 



