Correspondence — Mr. R. Craig. 285 



at Whitecliff Bay, but much thicker at Headon Hill and Hordwell 

 Cliff. These sands and clays form the Headon group ; they consist 

 of freshwater strata with bands of limestone and lignite, but in- 

 cluding numerous inconstant intercalations of layers containing 

 marine shells, for the most part much dwarfed. The age of the 

 Headon group, as shown by the fossils which it contains, is that of 

 "the zone of Cerithium concavum" of continental authors. 



The brackish-water Headon group is succeeded at Whitecliff Bay 

 by nearly 100 feet of purely marine strata. These marine beds, 

 which had been shown to rest on an eroded surface of the Headon 

 beds, contain the remarkable fauna which had been recognized by 

 many British and foreign geologists as that of the Lower Oligocene. 

 Similar strata with the same fossils are found in the New Forest, 

 at Lyndhurst, Brockenhurst, Roydon, and other points, and there 

 also attain a considerable thickness. It was pointed out that this 

 marine series is quite distinct from the Headon, or zone of Cerithium 

 concavum, with which it had been confounded. 



The author had been severely criticized for the views which 

 he had put forward in a former paper as to the manner in which 

 the Brockenhurst series is represented in the section at the west 

 end of the Isle of Wight. There was much difficulty in these 

 variable estuarine beds in correlating the beds seen in Colwell Bay 

 with those exposed in the cliffs of Headon Hill. With several pre- 

 vious authors on the subject, he maintained that the great series of 

 sandstones and limestones forming Warden Point and How Ledge 

 are continuous with those exposed in the face of Headon Hill, and, 

 consequently, that the marine beds of Colwell Bay overlying these 

 limestone series are younger than the brackish-water bands interstra- 

 tified with the Headon beds of Headon Hill. His critics, however, 

 insisted that these two beds agreed with one another in such a 

 manner that they must be regarded as parts of the same bed, sepa- 

 rated by denudation. In opposition to this view it was pointed out 

 that the Colwell-Bay bed is of the most inconstant character, and 

 long before reaching Headon Hill is seen to be on the point of- thin- 

 ning out and disappearing altogether. 



In conclusion, the author pointed out that his own interpretation 

 of the succession and correlation of the strata in the Hampshire 

 basin brings them into complete harmony with that which is main- 

 tained by the great majority of continental geologists, while that of 

 his critics appeared to be hopelessly irreconcileable with their views. 



coiaiaEsiPOiisrnDiEiisrciH]. 



FARTHER DISCOVERT OF MAMMOTH REMAINS AND ARCTIC 

 SHELLS, BELOW BOULDER-CLAT, NEAR KILMARNOCK. 

 Sir, — In the Geological Magazine, Vol. VI. p. 525, I reported 

 a find of Arctic shells, below 48 feet of Boulder-clay, in sinking a 

 pit, near to the old quarry, at Greenhill, Kilmaurs, where so many 

 Mammoth and Elk remains have been discovered. A like discovery, 

 of a Mammoth tusk, and Arctic shells, have just been made in a bed 



