1868.] TOPLEY BAS-noULONNAIS. 475 



With regard to the palacontological passage noticed above, it must 

 be remarked that wo have here fossils of a higher bed passing doM'n- 

 wards into a lower bed ; they cannot, therefore, have been washed 

 from one to the other, as might have been the case if Lower Green- 

 sand fossils were found passing up into the Gault. The general 

 fragmentary state of these fossils, at first sight, gives one the im- 

 pression that they really were derived from other beds. . It is rare to 

 find one entire, and they generally have a corroded appearance. 

 This is probably due to chemical action since their deposition. 



Prof. Way, who has made numerous analyses of the phosphatic 

 bodies from the Cretaceous beds, says, '•' that the phosphate of lime 

 has penetrated the various fossils and nodules fro^n tuithoat, there 

 scarcely exists the smallest question " *. 



3. Lower Greensand. — The masses of coarse sandstone which are 

 seen passing under the Gault at Wissant exactly correspond to the 

 upper part of the Folkestone Beds at Copt Point ; and there can be 

 no doubt of their representing the true Lower Greensand. In general 

 composition these blocks resemble those at Folkestone, but are finer- 

 grained, and appear to be somewhat richer in lime ; some of them 

 resemble coarse Kentish Eag. 



The Lower Greensand, at Caifiers, has already been noticed. It 

 l^robably extends all round the Boulonnais, excepting near Blacourt, 

 where Mr. Godwin-Austin f has observed the Gault resting on 



Fig. 3. — Section half a mile east of Desvres (about 4 miles). 



N.SO^W. S.SO°E. 



Riv. Liane. Haute Foret. Mont Hulin. 



a. Chalk and Upper Greensand. b. Gault. c. Lower Greensand. 



d. Wealden. e. Oolites. X X . Sea-level. 



Palaeozoic limestone. North of the Bois de Fiennes 1 saw, overlying 

 limestone, 12 feet of greenish and greyish sand, probably almost its 

 whole thickness here. The sand contains wood and scattered phos- 

 phatic nodules. Here, as at Caffiers, the Wealden beds are absent. 

 At Desvres the Lower Greensand occupies the higher parts of the 

 Haute Foret, overlying the Weald (see fig. 3). Immediately behind 

 the town, and to the north of it, is a pit showing 10 feet of false- 

 bedded whitish sand, underlain by ferruginous clayey sand, which 

 holds water and is probably Wealden. 



4. Neocomian Beds at Wissant. — M. Gaudry, in 1859 J, and M. 

 Lehon, in 1863 §, described a dark clay in the Wissant cliffs con- 

 taining Ostrea Leymerii. It is said to dip 35° (from the vertical) 



■* Journ. Roy. Agric. See. 1st ser. vol. ix. p. 84. 



t Quart. Journ. Geol. See. vol. xii. 1856, p. 68. 



I Bull. See. Geol. de France, ser. 2. tome xvii. p. 30. 



§ Ibid, tome xxi. p. 14. 



