110 . Mr Oscar Fraas' Observations on the Effects 



development. Why do they still give to many a genuine 

 German stratum an English name, which by its applica- 

 tion becomes false 1 I am certain that there exists no Brad- 

 ford clay either in Germany or in France ; that grey clay 

 of the south of England, at the top of the great oolite, 

 with its abundance of fine Apiocrinites intermedius^ elongatus, 

 and Parkinsoni, and with its numerous well-preserved tere- 

 bratulce, avtculcB, mi/ce, ^c. In Swabia we have nothing 

 similar ; the Bradford clays are a peculiar local formation of 

 the south of England. So it is with " Kimmeridge" and 

 " Portland ;" they are and remain local names, which cannot 

 be applied to the deposits of other localities. 



The names of the strata according to their fossils are of 

 greater value. In so far as the typical shells in the different 

 strata are the same, by comparison we soon arrive at some 

 degree of clearness ; but here also we meet with peculiar 

 difficulties, because those organisms which are leading in one 

 country, and which give the name to the stratum, disappear 

 from this stratum in other countries, appearing again as 

 typical characters in a higher or lower stratum. This is, 

 for instance, the case with Ammonites Parkinsoni ; in Swabia 

 it is the type for the stratum above A. coronatus, and beneath 

 A. macrocephalus ; in France and England it is the typical 

 shell in the lower oolite, and is followed by A. MurchisomB^ A. 

 Humphriesianus, and A. coronatus. In the same manner we can 

 neither use for France nor England such appellations so well 

 adapted to the German Jura rocks as amaltheus-hedSi opa- 

 linus-clays^ Jurensis-marls, Scyphiae-limQ^ione^, and others, 

 because the fossils referred to appear there either not at all, 

 or very rarely ; and other kinds of fossils are found which 

 characterise the stratum better. A synonymic examination 

 of the different stratum names is therefore necessary for the 

 comparison of the Jurassic rocks. 



These general views are followed by a very interesting 

 account of what he calls the German Jura formation, which 

 he describes in the following order, from below upwards. 



A. Black Jura or Lias — subdivided into — 1. Lower black 

 Jura (limestone of the lower lias shale). 2. Middle black 

 Jura (argillaceous Lias). 3. Upper black Jura (upper Lias 



