2 GEOLOGICAL MEMOIRS. 



was formed, and on account of recent deposits covering all the area 

 between the genuine Keuper and the Alpine sedimentary rocks. 



MM. Escher v. der Linth*, of Zurich, and P. Merianf, of Basle, 

 both of whom possess the knowledge and energy requisite for the 

 solution of this question, have lately visited the Vorarlberg, where 

 the genuine Cassian and Kossen beds begin to assume a more littoral 

 character, particularly conspicuous in the Cassian beds. These 

 eminent geologists succeeded further in finding out some relations 

 between the Keuper and the Cassian beds, which led them to seek 

 in the Upper Keuper for the equivalent of the Kossen beds. 



We now intend to give a description of certain strata occurring in 

 Suabia intercalated between the true Keuper and the lowest Lias 

 with Ammonites planorbis. These strata seem to us to offer some 

 remarkable analogies with the Kossen strata. 



In West Germany, France, and England the Keuper appears gene- 

 rally in the form of a great marl-deposit with local occurrences of 

 sandstone, gypsum, and dolomite beds of varying thickness. The 

 subdivision of the Keuper formation, as now in use, depends on local 

 petrographical diiferences. The Wirtemberg Keuper is considered 

 to be normally developed when its component beds (of a total thickness 

 of 700 feet) succeed each other in the following order : — 



6. Red Keuper marls; overlaid by the hard yellow sandstones of the Bone-bed. 



5. Sandstone (Stuben-sandstein). 



4. Marls with bands of sandstone. 



3. Argillaceous sandstones (fit for building-purposes). 



2. Variegated marls. 



1. Gypsum. 



(Dolomite ; generally ranked with the argillaceous coal series.) 



Such subdivisions offer exceptions even at short distances, one or 

 other of the beds disappearing; they may serve for practical pur- 

 poses or for local characters, but they are not adapted for tracing the 

 parallelism of strata for great distances. Many of the stratigraphical 

 characters undergo alteration on the opposite side of the Rhine ; 

 variegated marls (Marnes irisees) here become prevalent, and the 

 subordinate beds of heterogeneous rocks % occurring in it succeed in 

 an order quite different from that of the Wirtemberg beds. This is 

 still more conspicuous in the English Keuper. The coast of Ax- 

 mouth (Dorsetshire) presents high cliffs of denuded New Red 

 (Keuper) exclusively composed of variegated marls, not admitting 

 lines of separation analogous to those traceable in foreign Keuper 

 deposits. It has hitherto been impossible to make out in the Keuper 

 petrographical horizons which may be recognized in distant countries ; 

 nor have observers succeeded in establishing zones with determinate 

 and constant palseontological characters, indicative of coeval strata 

 wherever they may be met with. 



* '* Geologische Bemerkungen iiber Vorarlberg" in the Helvetian Transactions 

 for 1853 ; and Quart. Journ. Geol. Soc. vol. xi. part 2. Miscell. p. 16, &c. 



t In the " Verhandlungen der Basler naturforsch. Gesellschaft," 2 series, 

 Nos. 1 & 2, &c. ; and Quart. Journ. Geol. Soc. vol. xi. p. 451. 



X Dufrenoy & E. de Beaumont. — Explicat. de la Carte Geol. de la France, t. ii. 

 pp. 57, 58. 



