﻿Vol. 6 1.] CONTIGUOUS DEPOSITS OF GUAM ORGAN SHIKE. 393 



shales complete the Lower Rhgetic Stage, and pass up gradually into 

 a greyish-green marl. 



This marl-deposit was much fissured, previous to the deposition of 

 the superincumbent gritty limestone. Into these fissures gritty 

 material was washed. We have here a non-sequence caused by 

 a slight upheaval ; and, as a result, certain beds which are found 

 elsewhere, are not to be seen at Lavernock. The beds that 

 are missing at Lavernock measure at Garden Cliff about 13| feet. 

 Gradual subsidence, again, in the Lavernock area allowed of the 

 formation of the White Lias (fig. 2, p. 390). At Penarth, Etheridge 

 failed to discover ' Ostrea intus-striata, so common in Somersetshire 

 and Warwickshire ' ; 1 but at Lavernock it is not uncommon, and is 

 very abundant at Coldknap, Barry. The probable equivalent of the 

 Sun-Bed completes the series of limestone -beds ; and it is of this 

 stratum that I found bored pieces (crypts of LitJiophagus), on the 

 beach at Seven Sisters' Bay. The specimens of Ostrea liassica 

 (two) from this stratum were on the upper surface. The light- 

 coloured shales above the White-Lias limestones are grouped with 

 the White Lias ; they contain Ostrea liassica abundantly in the 

 lower portion. These are capped by the Paper-Shales, concerning 

 which there has been some debate as to whether they should be 

 classed with the Rhsetic or with the Lias. 2 I think that there is 

 little doubt but that they should be grouped with the Lias. 



The deposit between these shaly beds and the Lavernock Shales 

 requires no particular comment ; but there has been some doubt as 

 to the exact age of the last-named. However, as surmised by 

 Mr. H. B. Woodward, they belong to the angulata-zone, having 

 been laid down during the hemera marmorece. Oardinia ovalis 

 (Stutchbury) did not exist after this hemera. In the Lavernock 

 Shales it is abundant at certain horizons, both at Lavernock and at 

 Leckwithbridge, near Cardiff. At the latter locality SchJotlieimia 

 angulata (Schlotheim) and Cardinia ovalis occur in association; 

 consequently there can be no doubt as to the date of the beds. As 

 the Lavernock Shales are difficult to examine minutely at the typical 

 locality, the section at Leckwithbridge is appended : — 



Thickness in feet inches. 



Limestone, two beds mixed with"! ^ q 



marly clay about J 



Clay, marly, blue and yellow ... 8 



Limestone 2 



Clay, marly : 4 to G inches 5 



Limestone 3 f Ostrea irregularis, Lima 



Clay and limestone-bands 1 10 \ ( Plagiostoma ) aff. 



Limestone, dark grey 3 ( gigantea. 



Clay, hard, marly, reddish blotches 5 



1 Trans. Cardiff Nat. Soc. vol. iii (1870-71) pt. ii, p. 50. 



2 H. B. Woodward, ' The Jurassic Eocks of Britain ' Mem. Geol. Surv. 

 vol. iii (1893) p. 119. 



