462 HISTORY OF GEOLOGY AND PALAEONTOLOGY. 



differed from Alberti on certain points respecting the sub- 

 division, and the differences of opinion have been continued 

 by the adherents of the one view or the other until the present 

 day. The differences arose solely as to the best mode of treat- 

 ment of the passage-beds from Bunter to Muschelkalk, and 

 from Muschelkalk to Keuper The " Wellendolomit " or wavy- 

 surfaced dolomite, which occurs at the passage from the 

 Bunter sandstones to the typical limestones of the Muschel- 

 kalk group, were placed by Alberti at the base of the Mus- 

 chelkalk, whereas Quenstedt preferred to give them an 

 independent position, or to include them with the Bunter 

 sandstone. Again, the " Lettenkohle," or passage group 

 between Muschelkalk and Keuper, which comprises a series 

 of marls and clays with thin coal-seams, was placed by Alberti 

 at the base of the Keuper, and Quenstedt placed it as the 

 uppermost horizon of the Muschekalk. In later publications 

 both authors adhered to their opinions; Alberti made one 

 slight change in transferring the dolomitic limestone ("Tri- 

 gonodus limestone " of Sandberger) from its association with 

 the Muschelkalk to the base of his " Lettenkohle " group, thus 

 adding to the security of the systematic position to which he 

 had assigned the Lettenkohle group. 



As Alberti's sub-divisions have been fundamental in the 

 literature, and will be convenient for reference in the subjoined 

 pages, the list may be shortly stated : 



Upper 



Keuper 



Group, or 



" Gypsum 



Keuper." 



Lower 



Keuper or 



"Letten- 



kohlen " 



Group. 



SUB-DIVISION OF GERMAN 

 TRIAS. 



Tubingen sandstone (with 

 bone-beds). 



" Keuper" marls and arkose 

 sandstone, dolomitic marls, 

 " waterstones " (compact 

 sandstones), gypsum and 

 variegated marls. 



Upper limiting band of grey 

 dolomite and limestone, 

 dark clays, earthy coal 

 and sandstone, dark clays 

 and shales, earthy coal and 

 gypsum. 



PAL.EONTOLOGICAL 

 CHARACTER. 



(Afterwards distinguished as 

 Rhaetic or Infra-Lias): Avi- 

 cula contorta, Estheria 

 viinuta, Cardium Rhati- 

 cum, Belodon, Microksles 

 antiquus, etc. 



Occasional occurrences of 

 plant, fish, and labyrintho- 

 dont remains. 



Myophoria GoWfussi, M. 

 transversa, Lingula feint- 

 is sima, etc., Voltzia hetero- 

 phylla, Estheria minuta, 

 Bairdia; Fish and Saurian 

 remains. 



