128 MEETING OF THE BRITISH ASSOCIATION 



Witlingham, the spot in which the specimen figured by Dr. Wil- 

 liam Smith was said to have been obtained. The Mastodon appears 

 to be the only mammiferous animal which became extinct during 

 the crag epoch ; all the others at present discovered in that forma- 

 tion being either identical with existing species or with those found 

 in the more recent diluvial and lacustrine deposits. The author 

 next proceeded to notice the remains of birds which he had recently 

 procured from several localities in the crag district. These occur in 

 a highly mineralized state, and consist principally of bones belong- 

 ing to the extremities of natatorial tribes. The class of vertebrated 

 animals whose remains are met with in the greatest abundance is 

 that of fish. These, however, differ widely in their geological and 

 geographical distribution. Such as are found in the stratum which 

 contains the mammalia, consist principally of the hollow tubercles 

 of various species of Rays, with prodigious numbers of very singular 

 bones, which have externally very much the character of coprolites, 

 but which are thought, by Agassiz, to belong to the genus Platax, 

 or tropical fish. These bones are not met with in the crag of Es- 

 sex and the southern part of Suffolk, but throughout that part of 

 the formation the teeth of several genera of the Shark tribe occur 

 in considerable abundance. Of these the most remarkable is the 

 Carcharias megalodon, specimens of which are found as large as 

 those brought from the tertiary beds of Malta. The remains of rep- 

 tiles have not yet been discovered in the crag, which would rather 

 support the opinion advanced by Dr. Beck and M. Deshayes, that, 

 during the period of its formation, the climate resembled that of the 

 arctic regions. 



Mr. Murchison said he had come to a different conclusion as to 

 the great pebble on which the town was supposed to stand. In Ly- 

 ell's book, there were two little sections of that district, by which 

 it was clearly made out that the chalk rose up from the stratum in 

 immense masses. In conclusion, he begged to compliment Mr. 

 Charlesworth on his interesting paper. 



Mr. Bowman read some remarks on the Bone Cave of Cefn, in 

 Denbighshire, accompanied by some specimens; these caves have been 

 recently more extensively excavated. A section of the upper end of 

 the great cave consists, first, of a series of nearly horizontal layers 

 of impalpable adhesive loam of light and dark shades, in which 

 micaceous particles and layers of a redder colour may be seen. No 

 coprolites have been seen by Mr. Bowman, nor did he perceive any 

 teeth-marks of carnivorous animals upon the bone; and he confirmed 

 Mr. Stanley's opinion of a former lake, by citing the immense mass 

 of primitive diluvium on the side of the valley, and suggested the 

 importance of endeavouring to ascertain the height of its surface. 



A conversation took place on the benefit which would be derived 

 from the construction of accurate geological models, &c, of which 

 specimens were shewn by Mr. Ibbotson. 



Tuesday. — The first paper read was on the classification of the Old 

 Slate Rock of Devonshire, with an Explanation of the true position 



