206 GEOLOGY OF THE ISLE OF WIGHT. 



belong. Judging by the dip of tlie strata shown in these well:?, still 

 higher beds ought to be found on the top of the hill immediately 

 west of Dorehill — unless the gravel is exceptionally thick. This 

 seems to be the only place in the East Medina where there is any 

 likelihood of the Ostreo. ccdlifera beds being found, but there is 

 too much gravel to allow of a trial boring being made. 



At Wootton Station the cutting through Quarrels Copse 

 shows : — 



Feet, 

 Light-blue clay, with much ' race ' and concretionary stone with 



casts of Unio -....-- 5 

 Mottled red and blue clay .... about 20 



Fine sand, with water. 



25 



Several wells in the neighbourhood also ])enetrate the layers 

 immediately overlying the sand, but these beds are very sparingly 

 fossiliferous and yield little but bones of turtle. 



Many of the peculiar fossils of the Hamstead Series have 

 ah-eady been mentioned, and it only remains to give an outline of 

 the general character of the fauna and flora, and of the conditions 

 under which the beds were deposited. The main mass of the 

 Hamstead Series consists of mottled clays, probably deposited 

 in brackish-water lagoons. These, as is usually the case with the 

 mottled clays of the Oligocene groups, yield few fossils, except 

 bones of Turtle and Crocodile, and drifted plants. Interbedded 

 in the mottled clays, however, we find occasional seams of 

 Melania or Unio, or laminated clays with plants.* 



The blue clays are much more fossiliferous, yielding abundance 

 of shells — principally Unio, G yr en a, Paludina, Melania, Melanopsis, 

 and Nematura, with the addition of a few more estuarine forms, 

 such as Cerithium, Modiola, and i hja, on certain horizons. These, 

 with myriads of fruit of Follicu ites thalictroides and Carpolitkes 

 oimlum and seams of Entoinostrac i are the fossils commonly met 

 with in the Lower Hamstead Beds. 



The marine bands yield a much more characteristic fauna, 

 including a number of species quite unknown in the beds below. 

 It must be remembered, however, that there is no real break, but 

 that the next marine seam — that at the base of the Bembridge 

 Marls — IS fully three hundred feet lower, and its fauna is so 

 little known that we cannot compare the two. The only marine 

 beds that can be fairly compared are at the top of the Hamstead 

 Series and In the middle of the Headon Series — nearly five 

 hundred feet apart. 



Among the more abundant or peculiar of the marine shells 

 may be mentioned Ostrca cyathula and O. adlata, both confined to 

 this horizon ; Cytkerca Lyellii, Corhula pisum, C. vectensis, Cuma 

 Charle.nvorthii, Valuta Rathieri, Strehloceras and some species of 

 Cerithium, such as C. plicatian, C Sedgicichii, G. inornatum. 



* Sue also J. S. Gardner, Report Brit. Assoc, for 1887, p. 414. 



