200 J. F. BLAKE ON THE KIMMERIDGE CLAY OF ENGLAND. 



running E. and W. ; and the beds which skirt the bay may repre- 

 sent part of the above, though I cannot correlate them, and they are 

 themselves faulted so as to disturb the continuity. If, however, all 

 the beds here really lie below those described above, we should have 

 138 ft. more to add ; and some of them are certainly distinct, e. g. a 

 double hard sandy bed 1 ft. 9 in. thick, separated by dark papery 

 shales. Leaving these, however, out of consideration, we have in 

 the above section a continuous series of beds with the same kind of 

 lithological features, namely well- stratified shaly beds, differing in 

 this respect from the lower portions of the Kimmeridge Clay — fossi- 

 liferous at the top and bottom, and less so in the middle, but con- 

 taining Discina latissima and Lucina minuscula throughout, both 

 highly characteristic Upper Kimmeridge fossils, with abundance of 

 Cardium striatulum — Eccogyra virgula coming on below, and pro- 

 bably indicating that we are not far above the lower beds. Indeed 

 its occurrence with Discina latissima indicates a passage-bed from 

 one division to the other ; and therefore some portion at least of the 

 138 ft. in the bay ought rather to be classed as Lower Kimmeridge, 

 although if we are guided by the useful rule generally adopted in 

 the case of overlapping faunas to decide the name of the beds by 

 the lithological features, we should class them all with the upper. 



Be this as it may, all the beds from No. 40 upwards must cer- 

 tainly be reckoned as Upper Kimmeridge, and correspond to the 

 region of Discina latissima and Acanihoteuthis speciosa of Waagen, 

 which may thus reach, instead of 100 ft., as he states, a total thick- 

 ness of 650 ft. 



Buckland estimated the thickness here at 700 ft., which was pretty 

 near the truth ; for I have drawn the upper line in the midst of clays, 

 where they become fossiliferous, and are undoubtedly Kimmeridgian, 

 and some portion probably of the 138 ft. should be added below. 



Two zones of life may be remarked, the lower being characterized 

 by the presence of Amm. Thurmanni and Exogyra virgula, the upper 

 by a different set of the rarer fossils and the abundance of Astarte 

 lineata ; but these zones are not continuous over large areas. 



Going west to Bingstead Bay, whence Waagen took his section, 

 not more than 100 ft. of these beds appear ; but whether from their 

 non-existence, or the presence of another fault, not marked on the 

 Survey Map, is doubtful. At this level below the Portland Sand 

 the clay becomes uniform, without marked stratification, contains 

 Lower Kimmeridge fossils, and is quite different in appearance from 

 any further east. The whole cliff, however, is so broken that no 

 accurate knowledge can be really obtained of the thickness and lie 

 of the beds. 



Upper Kimmeridge, with bituminous shales, is known to occur in 

 Portland, though I doubt if some of the fossils quoted by Damon 

 really belong to it. 



In the inland counties * it is either very thin or absent, as there 

 is very little room for it at Swindon between the Lower Kim- 

 meridge and the Portland Sand, as is also the case at Hartwell ; 



* By inland counties I mean Wiltshire, Oxfordshire, and Buckinghamshire. 



