264 Prof. J. Buckman on the Combrash of the 



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 



65 

 An interesting feature in the natural history of the Brachio- 

 poda, is that five forms of Terebratula, namely the T. lagenalis, 

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

 Davidson's memoir on Oolitic Brachiopoda by the Palseontogra • 

 phic Society), are all referable to one species ; this is a fact ar- 

 rived at by a comparison of hundreds of individuals, and that 

 the author just cited seems to have almost arrived at when he 

 says, in his description of T. lagenalis, !' This species has little 

 to distinguish it from T. ornithocephala, into which it seems to 

 merge by insensible passages," p. 42. As regards T. sublage- 

 nalis, the same author remarks, u This species is always accom- 

 panied by T. lagenalis, of which it may perhaps only be a va- 

 riety/' p. 43 ; and further, " It is not difficult to find species 

 uniting ornithocephala to lagenalis, and this last to sublagenalis ; 

 but as the typical shapes of each are well distinguishable, it 

 will be found convenient to retain them under distinct specific 

 names." The Terebratula digona, he says, " often approaches in 

 general form and convexity certain specimens of T. obovata." 

 Here then a wide subject for discussion seems to be opened 



