CHALK. • 405 



Berkshire, Buckinghamshire, Oxfordshire, and Hertfordshire.' 

 It is now regarded as the upper limit of the Middle Chalk, and has 

 been recognized in the Isle of Wight, in Dorsetshire, and Bedford- 

 shire. The Chalk Rock consists of hard, blocky, cream-coloured 

 chalk, jointed perpendicularly to the plane of bedding, with lines 

 of irregularly-shaped, hard calcareo-phosphatic nodules, which are 

 green outside, but cream-coloured within. It contains Holastcr 

 planus, Ammoniies Prosperiamis, Scaphites Geinitzii, Lima ySpondylus) 

 spinosa, Turbo gcmmatiis, Rhynchonella plicatilis, Terehratula carnea, 

 T. semiglohosa, etc. 



Upper Chalk. 



This division, which is generally marked by numerous flint- 

 layers, contains however no flints in its upper part in Yorkshire, 

 and very few in the upper beds of East Kent. It is characterized 

 by Ananchytes ovatus"- ('Fairy or Sugar Loaf,' now, alas I termed 

 Echinocorys vulgaris by Dr. Wright, who has attempted to restore 

 an obsolete name), Galeriies cotiicus {G. albogalerus or Echinoconus, 

 — 'the Helmet'), Cyphosoma Koenigi ('the Shepherd's Crown'), 

 Micraster cor-angui?ium ('Fairy Heart'), Af. cor-bovis, M. cor- 

 testudinarium, Marsupites ornatus and M. Milleri ('Cluster stones' 

 or 'Tortoise encrinites'), Goniaster Parkinsoni, Bourgeficrinus 

 ellipticus, Tercbratula carnea, T. obesa, Rhynchonella plicatilis, 

 Magas puinila, Crania Parisiensis , Pecten nitidus, Lima {Spojidylus) 

 spinosa, L. Hopcri, Pleurotomaria perspectiva, Belemnilella mucronata, 

 B. quadrata, Baculites Faujasii, B. anceps, Siphonia (^Choanites) 

 Koenigi, Ventriculites radiatus, etc. Ammonites are not common. 

 Remains of Mosasaurus occur at Norwich and other localities. 



The ' Upper Chalk ' is a somewhat vague term ; for, as Mr. Godwin-Austen 

 has remarked, there is no portion of the formation in tliis country which has not 

 been greatly denuded.^ 



YORKSHIRE. 



The Chalk extends from Flamborough Head inland, forming the 

 Yorkshire Wolds. On the coast it is difficult to study the various 

 divisions (see p. 402), as the sea in several places washes the almost 

 vertical cliff's, which at Flamborough Head rise to a height of about 

 400 feet. The base of the Chalk is well shown in Speeton Cliff", 

 where there are alternations of red, grey, and white chalk above 

 the bottom Red Chalk proper. Some beds of the grey chalk are 

 very arenaceous, containing in one instance, according to Prof. 

 J. F. Blake, as much as 25 per cent, of alumina, iron, and insoluble 

 matter. The red colour does not coincide with the stratification, 



' Q. J. xvii. 166 ; see also C. Barrois, Ann. Soc. Geol. du Nord, iii. 145 ; 

 Penning and Jukes-Browne, Geol. Cambridge, p. 69. 



■ The generic name is derived from the Greek, d, not, a-yx^^, to press tight, and 

 signifies not pressed (Owen). 



3 Proc. G. S. iv. 168 ; G. Mag. 1865, p. 199. 



