250 



EEV. W. E. A]S T DEEWS ON THE 



" At the top of the Lower Purbecks and in the Middle Purbecks 

 much useful stone occurs, and has been extensively quarried both 

 for building-purposes and for burning into superior lime ; from these 

 exposures some interesting fossils have been obtained. 



" Thick beds of a hard grey marl at the top of the Purbecks, very 

 similar in appearance to the insect-beds of Durlston, but containing 

 Cy prides, here afforded some few insect-remains, several species (6) 

 of fishes, and ArcJiceoniscus (the fishes are the following — 



Microdon radiatus, Ophiopsis breviceps) ; 



Pleuropholis, 



also Turtle and Crocodile remains. The insect-remains are not so 

 plentiful as at Durlston, a comparative scarcity arising from the 

 terrestrial condition of these beds in the Yale of Wardour, as evi- 

 denced by the presence of Cyprides. 



" Passing up through the " cherty freshwater " beds, which here 

 contain, as in Dorsetshire, Pethidines and Cyclades beautifully imbed- 

 ded in flint, we arrive at one of the most interesting beds of the whole 

 series, a marine bed called, in the island, the " Cinder." Although 

 it is much reduced in thickness from 12 ft., crowded with Ostrea 

 distorta, still, in the Yale of Wardour, it maintains its marine cha- 

 racter, and, as elsewhere, from its hard enduring nature, has outlasted 

 many softer beds. Beside the Ostrea distorta which is scattered 

 through it, two species of Trigonia occur, T. gibbosei and a new 

 species which Mr. Etheridge has named T. densinoda, which has not 

 occurred in any other formation and, according to Mr. Etheridge, is 

 of much palseontological interest, arising from the fact that it has 

 characters connecting it with the Jurassic Trigonia-gmwp Grlabrae, 

 on the one hand, and Cretaceous forms of the group Quadratse, on 

 the other. Occurring, as it does, in beds of a transitional character 

 between the Jurassic and Cretaceous, it is more interesting still. 



"Higher up in the Middle Purbecks occurs an extraordinary abun- 

 dance of the fossil Isopod Archeeoniscus Brodiei, sometimes so closely 

 lying together that 250 specimens have been obtained on a slab not 

 larger than one foot square. The 8 or 10 feet of red and yellow 

 stratified sandy clays which are here found on the top of the Pur- 

 becks, are possibly the Wealden. They rest upon an eroded surface 

 of limestone, but otherwise present no unconformity. It is remarkable 

 that these Wealden beds so often cap the Purbeck series, a fact 

 that seems to indicate that the same area which served for the delta of 

 the Purbecks performed the same office for the Hastings series, with, 

 however, this difference — that the source from which the materials 

 came must have been different, although the ancient river may 

 have served for both formations. 



" Endogenites erosa, not hitherto clearly proved to belong to any 

 other horizon than the "Wealden, has been found in these red and 

 yellow sandy clays in situ ; a stratified bed above contains a small 

 Modiola and Cyrena ; but whether Wealden or Purbeck, I am not 

 able to say. Endogenites erosa occurs in a similar section half a 

 mile to the east." 



