THE CHALK 45 



should try this locality but those who can be trusted to 

 take proper care on the top of a precipice. When a high 

 wind is blowing the position may be especially dangerous. 

 The Chloritic Marl is followed by the Chalk Marl, of 

 much greater thickness. This consists of alternations of 

 chalk with bands of Marl, and contains glauconite and 

 also phosphatic nodules in the lower part. Upwards it 

 merges into the Grey Chalk, a more massive rock, coloured 

 grey from admixture of clayey matter. These form the 

 Lower Chalk, the first of the three divisions into which 

 the Chalk is usually divided. Above this come the Middle 

 and Upper, which together form the White Chalk. They 

 are much purer white than the lower division, which is 

 creamy or grey in colour. The Chalk Marl and Grey 

 Chalk are well seen at the Culver Cliff, and run out in 

 ledges on the shore. The lower part of this division is the 

 most fossiliferous, and contains various species of Am- 

 monities, Turrilites, Nautilus, and other Cephalopoda. 

 (Of Ammonites Schloenbachia varians is characteristic. 

 Also may be named S. Coupei, Mantdliceras mantelli, 

 Metacanthoplites rotomagensis, Calycoceras naviculare, 

 the small Ammonoid Scaphites aequalis ; and of Pectens, 

 Mquipecten beaveri and Syncyclonema orbicularis may be 

 mentioned). White meandering lines of the sponge 

 Plocoscyphia. labrosa are conspicuous in the lower beds. 

 The Chalk Marl is well shown at Gore Cliff, sloping upwards 

 from the flat ledges of the Chloritic Marl. It may be 

 studied well, and fossils found, in the cliff on the Ventnor 

 side of Bonchurch Cove, which has all slipped down 

 from a higher level. 



The uppermost strata of the Lower Chalk are known 

 as the Belemnite Marls. They are dark marly bands, in 

 which a Belemnite, Actinocamax plenus, is found. The 

 hard bands known as Melbourn Rock and Chalk Rock, 

 which on the mainland mark the top of the Lower and 

 Middle Chalk respectively, are neither of them well marked 



