EH^TIC SYSTEM. 



II.— RH^TIC SYSTEM. 



The sediments between tlie uppermost Keuper beds and the 

 lowest strata of the Lias are by many authors included in 

 the Triassic system,' but by others the Ehcetic series is 

 regarded as forming the base of the Jurassic system.'' The 

 occurrence of particularly rich and well-preserved floras in beds 

 ■of Rhsetic age near Baireuth, Bamberg, and other localities in 

 Franconia, in the coal-bearing strata of Scania, and in other 

 regions, has brought this period into prominence as one that is 

 of special importance from a palseobotanical standpoint. In 

 Britain the Khsetic strata form a thin band stretching diagonally 

 across England from near Kedcar on the Yorkshire coast to 

 the cliffs of Dorsetshire. Kocks of this period are probably 

 represented in the outlying patch of Lower Lias beds to the 

 west of Carlisle ; ^ Rhsetic beds occur also in the north-east of 

 Ireland and in the north of Scotland. 



The vegetation of the land bordering the shallow Ehsetic 

 sea is represented in the British area by a few fragmentary 

 fossils, which afford a striking contrast to the richness of the 

 plant-beds of this period in other parts of the world. 



The line of division between the base of the Lias and the 

 summit of the Ehsetic is not very well defined, and the difficulty 

 ■of distinguishing between beds of Upper Ehsetic and of Lower 

 Liassic age is increased by the common use of a misleading 

 terminology. The Ehsetic series is often subdivided into three 

 stages, the White Lias at the top, succeeded by the Black 

 shales and Grey marls. The term White Lias, as pointed out 

 by Mr. E. WUson,* is an unfortunate one ; it has been applied 



1 Geikie (93), p. 867 ; Blanford (84), p. 318. 



2 De Lapparent (00). 



3 Holmes (81), (99). 

 * Wilson, E. (91). 



