﻿Mr. W. Whitaker on the Chalk of Dorset and Devon, 547 



Two new forms, differing generically from the above, but pro- 

 bably referable to the same family (the Portunidce), were described, 

 under the name of Bhachisoma (g. n.), JR. echinata and R. hispinosa. 



A third form, belonging to the Corystidae, was then noticed. This 

 family, represented in the fossil state by the genus Palceocorystes, is 

 well known in the Gault and Upper Greensand of Folkestone and 

 Cambridge, one species ranging up as high as the Maestricht beds. 

 The occurrence of Palceocorystes in the Lower Eocene is of great 

 interest. Mr. Woodward named this new Palceocorystes P. glabra. 



3. " On the Chalk of the Cliffs from Seaford to Eastbourne, 

 Sussex." By W. Whitaker, Esq., B.A., F.G.S. 



The author compared the chalk of the Sussex coast with that of 

 the Kentish coast, and stated that it consisted of the following divi- 

 sions in descending order : — 



1. Chalk with flints, of great thickness. 



2. Chalk with flints and nodular layers, weathering rough. 



3. Chalk without flints, but with nodular layers, weathering rough. 



4. Thick-bedded massive chalk without flints. 



5. More thinly bedded chalk without flints, but with marly beds. 



6. Chalk-marl, 50 or 60 feet. 



The highest of these divisions stretches as far eastwards as Beachy 

 Head, and forms the whole of the cliffs to within a short distance of 

 that point. 



4. " On the Chalk of the southern part of Dorset and Devon." 

 By W. Whitaker, Esq., B.A., F.G.S. 



The divisions of the Chalk we^e traced by the author westward 

 from cliffs on the north side of Swa- age Bay to beyond Beer Head 

 in Devonshire. First the succession of the beds was shown to be 

 as in the Isle of Wight, namely : — 



4. Chalk without flints. 



5. Chalk-marl. 



1. Chalk with flints, very thick. 



2. Chalk with few flints. 



3. Chalk-rock, very thinly developed. 

 It was shown that the lower beds became thinner westward, 



until, at one part of the Beer-Head section, the chalk with flints 

 rested at once on the Upper Greensand ; and the following general 

 conclusions were drawn : — 



That the chalk-marl thins westward, and its bottom part becomes 

 marked by the presence of quartz-grains, showing perhaps signs of 

 a less deep-sea character than usual. 



That the chalk without flints thins westward (from about 200 

 feet in the Isle of Wight) until, in Devonshire, it is but 30 feet 

 thick, or even less. 



The consequent nearness of the chalk with flints to the Greensand 

 helps to explain the deposits of flints on some of the Devonshire hills. 



Jan. 11. — Joseph Prestwich, Esq. F.R.S., President, in the Chair. 

 The following communications were read : — 

 1. " On the older Metamorphic Bocks and Granite of Banffshire." 

 By T. F. Jamieson, Esq., F.G.S. 



The author indicated three divisions in the metamorphic strata of 



