26 GEOLOGICAL MEMOIRS. 



marl, and differing from the much deeper black limestones of the 

 variegated sandstone (now called *' Guttenstem Strata" by Fr. von 

 Hauer) by their want of lamination, and by the abundance of fossils, 

 especially of Brachiopods and other Bivalves, contained in them. 

 Hence the name of " Koessen Strata" was applied to the Gervillia- 

 and Avicula-limestone near Bad Kreuth, described by Von Buch 

 (Abhandl. d. Berlin. Akad. 1827, p. 82), to the lias limestone of the 

 Mertlbach (Gaisau) as represented by Messrs. Sedgwick, Murchison, 

 and Lill de Lilienbach in the last author's second section, and espe- 

 cially to the whole formation called Gervillia-strata by MM. Emmrich 

 and Schafhautl. 



The comparison of the numerous fossils soon proved these Koes- 

 sen beds to be part of the lias; and subsequent palseontological re- 

 searches introduced a great change in the limits originally assigned 

 to the above term. Rocks, apparently quite similar as to their ex- 

 terior aspect, were shut out on account of their aberrant palseonto- 

 logical character, and others, of completely different petrographical 

 character, but concordant by their fossil contents, were comprised 

 in the Koessen group. I will now attempt a brief sketch of the 

 separate members of the group : the study of the whole cannot fail to 

 show that an exact investigation of fossils is only the sure foundation 

 for a correct knowledge of our calcareous Alps. 



I. Koessen Strata^ properly so called. 



Synonyms : — Upper St. Cassian, t'^, Escher and Merian ; Gervillia 

 Limestones, Emmrich ; Gervillia Limestones and Slates of the 

 Whetstone Formation, Schafhautl. 



These strata are generally black, and differ, by the characters above 

 mentioned, from the Guttenstein strata which belong to the muschel- 

 kalk. Other similar black limestones, containing Brachiopods of 

 the upper lias (Hierlatz strata), e. g. those of the Stambachgraben 

 near Goisern, must be carefully separated from them. 



The genuine liassic Brachiopods contained in these strata are, — 

 Spirifer rostratus, Schloth., Sp. Muensteri, Dav., Terebratula cor- 

 nuta, Sow., and Rhynchonella obtusifrons, Sss. Of other genera I 

 quote for the most part on Von Hauer' s authority, — Nucula com- 

 planata, Phill., Pinna folium. Young and Bird, Lima gigantea. Sow., 

 Pecten liasinus, Nyst. 



According to M. Stur's investigation, these strata near Schloss 

 Enzesfeld are in close connexion with a yellowish-brown limestone, 

 containing, together with the same species of Brachiopods, a notable 

 number of lower liassic remains of genera rarely met with elsewhere 

 in the Koessen strata. Such are, as Von Hauer kindly commu- 

 nicated to me. Ammonites bisulcatus, Brug., Amm. obliquicostatus, 

 Ziet., Amm. Kridion^ Hehl., Amm. Moreanus, d'Orb., and Pleuro- 

 tomaria expansa, Goldf. 



The numerous localities which afford the above-mentioned Bra- 

 chiopods are sufficient to point out the extraordinary geographical 

 range of these strata. Without reckoning the localities recently dis- 



