London Clay. 245 



sists of brown and bluish-grey clay, with occasional 

 bands of calcareous concretions (septaria). In the 

 London basin it varies in thickness from 50 feet in the 

 extreme west, at Newbury, to 480 feet in Essex. In the 

 Isle of Wight, at Alum Bay, it is only 200 feet thick 

 (fig. 47) ; in Whitecliff Bay, 295 feet ; and at the west 

 extremity of that basin, in Dorsetshire, it dwindles away, 

 being barely distinguishable except to well-accustomed 

 eyes. The chief fossiliferous locality in the Hampshire 

 basin is at Bognor in Sussex. In the Isle of Wight 

 fossils are scarce in this formation. Eound London they 

 occur at Highgate, and in other places far to the west. 

 The Isle of Sheppey has long been famous for its fossils, 

 being found there chiefly because of the frequent 

 landslips from the cliffy slopes that overlook the estuary 

 of the Thames. The plants have long been celebrated, 

 consisting of various Palm-nuts, Nipadites ellipticus, 

 and N. umbonatus, and other fruits ; Conifera?, many 

 leguminous plants, laurels, figs, junipers, and plants of 

 the citron tribe, are also common, all of extinct species. 

 Eemains occur of birds allied to the vulture (Lith- 

 ornis vulturinus) and king-fisher (Halcyornis toliapi- 

 cus\ and a small swimming-bird, described by Owen, 

 with tooth-like serratures on the bill ; turtles and river 

 tortoises are numerous of the genera Chelone (breviceps, 

 &c.), Emys (Conybeari, &c.), Platemys, and Trionyx] 

 also a crocodile (Crocodilus champsoides) and snakes 

 (Palceophis toUapicus and P. longus). Terrestrial 

 mammals also occur a Marsupial (Didelphis Col- 

 chesteri), a Bat, and Hyracotherium cuniculus ; also 

 Miolophus planiceps, Pliolophus vulpiceps, and 

 Coryphodon eoccenus, which are tapir-like animals, in a 

 distant way allied to the tapirs now found on the 

 banks of South American rivers. 



