PRESTWICH BRITISH AND FOREIGN TERTIARIES. 99 



certain distinguishing features : in descending order, these divisions 



are — 



Feet. 



4. Compact white marls, passing down into beds alternating 

 with greenish marls and thin yellow limestones, with 

 seams of chert; a few freshwater and brackish-water 

 fossils sparingly distributed. Average thickness about 20 



3. Thin-bedded and fissile calcareous flags and sandstones 

 alternating with white marls and limestones; charac- 

 terized in places by a profusion of aestuarine shells alter- 

 nating with some freshwater forms about 15 



2. The thick main mass of soft, light-yellow, calcareous free- 

 stone, passing in places into calcareous sands, rich in 

 marine organic remains about 40 



1. Variable beds of more or less calcareous green sands, 

 sometimes concreted ; often flint-pebbles at base. Ma- 

 rine fossils numerous only in places, — more generally 

 absent about 25 



Mean dimensions 100 



In England the general sections and approximate dimensions of 

 the Bracklesham Sands may be taken as under. 



1. Section in descending order at White Cliff Bay, Isle of Wight. 



Feet. 



c. Grey clay and green sands, with subordinate brown clays, 

 yellow sands, and some small ])ebble-bands and lignites ; 

 vegetable impressions and shells occasionally numerous. . 135 



b. Thick-bedded, slightly calcareous, green sands abounding 

 in fossils ; with a central mass of grey and brown clays, 

 with lignites 190 



a. Beds of laminated grey and brownish clays, yellow sands 

 and some green sands; comparatively few shells, nume- 

 rous vegetable impressions, and a few small beds of lig- 

 nite; layer of large flint-pebbles, 1 to 2 ft. thick, at base. 123 



448 



2. The section of the same series at Alum Bay is as follows : — 



Feet. 

 Alternating thick beds of bright-coloured (yellow, white, 

 ochreous, brown, and red) siliceous sands, tough grey 

 brown and black clays ; with subordinate foliated white, 

 pink, and yellow clays, pebble-seams, and beds of hgnite ; 

 no animal organic remains 564 



[For fuller details see my paper in Journ. Geol. Soc. vol. ii. 

 pp. 252-258. The White Cliff" section includes strata from 

 6 to 14 (excepting the upper 9 feet), and Alum Bay from 

 15 to 28, of the sections there given.] 



To determine to what extent the French series indicates a commu- 

 nity of origin with the English series, we must not take each only as 

 a whole, separately and entire in itself, but rather search if there are 

 not concurrent characters which show them to belong to disjointed 

 parts of one body. We must follow each division of the Calcaire 



H 2 



