3I00EE AB>'0E5rAL SECOXDAET DEPOSITS. 511 



A. angulatvs, to whicli has been accorded a special horizon be- 

 tween the zone of A.planorhis and that oi A. Bucllandi, is really the 

 prevailing shell in the latter around Bath, where it sometimes 

 reaches a great size. In a garden near the railway station at 

 Keynsham, there is a specimen which attains o feet 10 inches in 

 cii'cnmference, and 2 feet in diameter. This species is quite common 

 at Sontherndown, where also, in a garden leading down to the chffs, 

 is a very large specimen ; and in its young form it may be seen to 

 pass up into the very highest beds at Bridgend, where it is found 

 associated with A. seinicostatus and A. Sauzianus. A. Becliei, from 

 the base of the Middle Lias, passes thi'ough that formation, whilst 

 A. radians, A. variahiJis, and A. JJoorei of t^e ITpper Lias, the dis- 

 covery of which in the sands of the Inferior Oolite suggested the 

 removal of the latter beds to the Lias, are with other species found 

 as low down as the !Marlstone of the Middle Lias. 



Pecten PoUiuv occurs as a dwarf form in the Ehcetic "WTiite 

 Lias, and passes uninterruptedly in association with Ostrea arietis 

 (0. midticosfata, Terq.), Plicahda acuminata, and other Sutton and 

 " Infralias '"' species through all the Lower Lias to the A.-Buddandi 

 beds ; and I know of no single locality, on whatever horizon, where 

 more or less frequently these species are not to be found. Xot only is 

 this so, but the general " Infralias " fauna passes up into the A.- 

 Budlandi beds at Bath and Keynsham, the limit to tlieir discovery in 

 the veiy highest beds at these places being evidently determined by 

 the denser character of the matrix, which prevents their weathering 

 out. The •' InfL'ahas '' fauna will be found again in the highest beds 

 at Sontherndown and Bridgend, accompanied by Grtfjdia^a incurva. 

 The latter shell is to be found abundantly with the Coral-fauna of 

 Brocastle, through the Sutton and the greater part of the Bridgend 

 section, and is shown in the Camel section to have been contempo- 

 raneous with Ammonites planorhis. 



These passages might be multipHed ; but they are sufficient to 

 show that although in a special locality we may arrive at correct con- 

 clusions regarding the range of genera and species, yet where a 

 wider area is considered, and especially should the beds in which 

 the fossils are found have been deposited under chfferent ciixum- 

 stances, they will not be found coiTect. 



YI. The Souih YrALzs Disteict. 



Having pointed out the peculiar characters of the Secondaiy de- 

 posits connected with the Mendips and the Somersetshire coal-basin, 

 I now proceed to a consideration of similar phenomena on the southern 

 edge of the coal-basin of South "Wales. 



It has before been stated that the ui^heaval of the Old Bed 

 Sandstone and Carboniferous beds of South Wales was probably 

 contemporaneous with that of those of the Mendips, of which they 

 form a natural continuation ; and such being the case, it might be 

 expected that in association with them similar abnormal conditions 

 would be observed. 



I have not given a critical examination to the whole district, 



