XVI PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



taceous beds, and the author defines it more strictly as occurring 

 between the Kimmeridge and lower Neocomian beds. It refers to 

 certain Alpine deposits containing Cephalopoda, probably corre- 

 sponding with Portland, Purbeck, and Wealden beds, but of which the 

 exact parallelism has not yet been sufficiently made out. 



" On the Fauna of the St. Cassianbeds, being a Supplement to the 

 Palaeontology of the Trias of the Alps," by Gustav Laube, in two 

 parts, the first of which contains a description of the Sjpongitaria, 

 Corals, Echinidce, and Crinoidce, with 10 plates; the second part 

 contains the Brachiojpoda and Bivalves, also with 10 plates. 



" The position of the Raibl beds in the Franconian and Suabian 

 Keuper," by Prof. F. Sandberger. 



With reference to the much discussed question of the true position 

 of the Avicula-Gontorta beds, to which I alluded on a former occa- 

 sion, I find in the ' Bulletin de la Societe Geologique de France,' 

 2nd ser. vol. x-xii. p. 369, an interesting communication by M. Jules 

 Martin, entitled " The Ehaetic formation or Avicula-contorta zone ; 

 its petrographical, stratigraphical, and palaeontological constitution 

 in the different parts of Europe where it has been studied." Dis- 

 satisfied with many of the results of previous investigations, M. 

 Martin determined to go fully into the whole question, the result 

 of which has since been published. In the meantime he here 

 gave a general resume of what appeared to him the real state of the 

 case, after examining the data observed in diiferent countries in 

 a mineralogical, stratigraphical, and palaeontological point of view. 



After describing the mineralogical character of the beds in question 

 in different parts of Europe, he comes to the conclusion that the 

 petrographical constitution of the zone is always dependent on the 

 nature of the underlying beds, or of the coasts which were washed 

 by the seas of this distant period. A coarse sandy conglomerate 

 when in contact with the crystalline rocks, becomes a fine sand 

 when it succeeds the grit of the Keuper, and marly limestone when 

 it rests upon the variegated marls and other argillaceous beds. Thus 

 it often happens that the lower beds resemble, and even alternate 

 with, the Keuper for a certain time, and then in the upper portion 

 pass by a regular transition into the overlying Lias. Mineralogically, 

 therefore, there is no evidence to show that it belongs to the Lias or 

 to the Keuper absolutely. 



The same may be said respecting the stratigraphical evidence. 

 With the exception of a few local cases of a very limited character, 

 there does not appear to have been any violent or cataclysmal dis- 

 turbance, either at the. beginning or at the end of the Avicula-con- 

 torta period. In general, these beds are found to be in a position of 

 conformable stratification, both with the Keuper and with the Lias. 



The palaeontological evidence is more important. M. Martin has 

 carefully examined all the lists given by the different authors who 

 have written on the subject, and endeavours to show how many 

 species and genera are common to the Keuper and the Avicula-con- 

 torta zone, how many are peculiar to this zone, and how many it 

 contains in common With -the overlying Lias. After eliminating 



