102 THE RHuETIC PERIOD. CHAP 



the sea previously unknown. To the upper part of this series, the 

 Kossen group, the term Rhsetic or Upper Trias is now commonly 

 applied ; and it is generally admitted that some at least of the 

 lowest English and Irish beds of what was formerly called lias must 

 be put in the same class. 



The Ehsetic strata preserve a nearly uniform thickness over 

 considerable spaces, and are perfectly conformable to the poikilitic 

 series below, and to the liassic series above. In regard to their 

 many thin parallel strata, and the state of the iron oxide, and the 

 abundance of iron sulphide, they resemble the lias, and may be 

 regarded as brought into the sea of the period by currents different 

 from those which supplied the red sediments, and dependent on 

 distant earth movements. They appear to have been deposited 

 in shallow water, liable to dryness, and possibly to the occurrence 

 of brackish if not fresh water, as in the case of the Estheria bed, 

 which contains plant remains of a group resembling fresh-water 

 Naiadacese. 



Though not seen in the drainage of the Thames, these interesting 

 strata intermediate in position between the poikilitic and the 

 liassic deposits occur in the Vale of Severn, and in the country 

 near Stratford-on-Avon. They may be well and conveniently ex- 

 amined in Garden Cliff, at Westbury-on-Severn. Several descrip- 

 tions by excellent observers have been published of this admirable 

 natural section. The following, prepared after repeated examina- 

 tion by Mr. J. E. Lee and myself, differs little from those given 

 by Dr. Wright and Mr. Etheridge a : 



KELETIC. 



Grey shale and thin skerry laminae . 9 o 

 White and grey limestone, -i 



lumpy and laminated \- .09 Estheria : Naiadites. 



Clay and thin limestone below J 



a Memoirs of Pal. Soc., 1862, pp. 69, 70. 



