326 Prof. J. Buckmau on the Cornbrash of the 



These analyses show that the phosphoric acid and sulphate of 

 lime — two important chemical agents in the growth of crops — 

 greatly predominate in the Cornbrash ; and besides this, the thick- 

 ness of Cornbrash soil is always greater than that upon the 

 Stonebrashes, as this rock more readily breaks up and becomes 

 disintegrated by atmospheric action. 



These remarks tend to show the great practical advantage of 

 geological and chemical knowledge, and fully explain how a 

 successful farmer near Cirencester has converted a " brash farm " 

 — which is in general a term of reproach — into one of the most 

 productive farms in the district, this brash being the fertile Corn- 

 brash. 



But not only is this thin stratum of interest on account of 

 the fine crops which it yields, but it will ever present a 

 charm to the geologist from the rich harvest of fossils which it 

 everywhere contains ; indeed, the reason why it crumbles down 

 so readily is probably owing in part to its being composed of 

 shells, which are merely cemented together by a calcareous ma- 

 trix, whilst the phosphates of the rocks are doubtless derived 

 from its imbedded animal matter ; hence our examination has not 

 only afforded a tolerable list of species, but several forms are 

 numerically so great, and offer so many curious types, as to de- 

 serve a more attentive study than has yet been accorded them. 

 Now in giving an account of the fossil contents of the Cornbrash^ 

 it must be understood that my facts are solely derived from ob- 

 servation in the quarries of my more immediate district and are 

 consequently incomplete, and as a lengthened list of fossils could 

 only be the more tedious the more copious its details, I pro- 

 pose in this place to append a mere summary of its remains, 

 making remarks upon its more interesting palseontological 

 features. 



Summary of Cornbrash Fossils from the neighbourhood of 

 Cirencester. 



Species. 



1. Brachiopoda 7 



2. Conchifera .30 



3. Gasteropoda 10 



4. Cephalopoda 3 



5. Annelida 4 



6. Zoophyta 3 



7. Echinodermata 8 



An interesting feature in the natural history of the Brachio- 

 poda, is that five forms of Terehratula, namely the T. lagenalisy 

 sublagenalis, obovata, ornithocephala, and digona of authors (see 

 Davidson's memoir on Oolitic Brachiopoda by the Palseontogra- 



