ATHERFIELD CLAY. 
309 
and calcareous stone forms strata two feet thick, alternating 
with quartzose sand. The total thickness of these Folkestone 
and Hythe beds is less than 300 feet, and they are seen to 
rest immediately on a gray clay, to which we shall presently 
allude as the Atlierfield clay. Among the fossils of the Folke¬ 
stone and Hythe beds we may mention Nautilus plicatus 
(Fig. 277), Ancyloceras {Scaphites) gigas (Fig. 278), which 
Fig. 2TT. Fig. 278. 
Nautilus plicatus, Sow., in 
Fitton’s Monog. Ancyloceras gigas, D’Orb. 
has been aptly described as an Ammonite more or less un¬ 
coiled; Trigonia caudata (Fig. 280), Gervillia anceps (Fig. 
279), a bivalve genus allied to Avicula, and Terebratula sella 
(Fig. 281). In ferruginous beds of the same age in Wiltshire 
is found a remarkable shell called Diceras Lonsdalii (Fig. 
282, p. 309), which abounds in the Upper and Middle Neo- 
comian of Southern Europe. This genus is closely allied to 
Chama, and the cast of the interior has been compared to the 
horns of a goat. 
Fig. 279. Fig. 280. 
Gervillia ancejys, Desh. Upper Trigonia caudata, Agass. 
Neocomian, Surrey. Upper Neocomian. 
Atherfield Clay.- —We mentioned before that the Folke¬ 
stone and Hythe series rest on a gray clay. This clay is 
only of slight thickness in Kent and Surrey, but acquires 
great dimensions at Atherfield, in the Isle of Wight. The 
difference, indeed, in mineral character and thickness of the 
Upper Neocomian formation near Folkestone, and the cor¬ 
responding beds in the south of the Isle of Wight, about 
