TRANSACTIONS OF THE SECTIONS. &i 



clined carboniferous limestone at the south-eastern extremity of Durd- 

 ham Down, near Bristol. 



Having in the memoir read some time since before the Geological 

 Society entered into the particular characters of this formation, it is 

 not necessary here to repeat them further than to show the proofs of 

 this deposit being formed upon the spot, and not the effect of accumu- 

 lated drift. 



" In all the dolomitic formations we have been enabled to examine in 

 this neighbourhood, we find them composed of fragments of the rock 

 on which they rest. These observations equally apjily to the conglo- 

 merate beds of the new red sandstone. For instance, in the quarry 

 from whence these bones have been recovered, fragments of the lime- 

 stone only upon which it rests are found. In the beds which rest upon 

 the old red sandstone, such as those of Ham Green, Valley of Kein, 

 Thornbury, &c., it is found to be composed of quartzose pebbles, frag- 

 ments of friable sandstone, and limestone boulders, in fact the precise 

 components of the conglomerate beds of the old red sandstone which 

 they immediately overlie. In the conglomerate or brecciated beds of 

 the new red, which occur in the New Cut or River, and flank Brandon 

 Hill, are found pebbles of quartz and of compact millstone grit, pre- 

 cisely identical with the formation of Brandon Hill itself. 



" From these facts it naturally follows that the animals were destroyed 

 at a period of great local disturbance without transport from a distance 

 or great movement. If the latter had taken place the bones would 

 have been distributed over a large space, and not as now confined to a 

 spot not exceeding half an acre in extent ; besides which, although 

 the limestone and bones themselves were dislocated and fractured to a 

 great extent, still there is no evidence of abrasion. 



"That the magnesian cementing paste was once subtile and fluid is 

 exhibited in all the bones, and beautifully evidenced in a fragment of 

 jaw which is exhibited to the Section, in which wiU. be seen the sub- 

 maxillary canal, filled as if injected, also the alveoli of the jaw, hollows 

 of the teeth, &c. That it quickly became viscid and tenacious is also 

 evidenced by its holding up in its substance the portions of bones and 

 fragments of limestone even of great weight, while smaller portions had 

 gravitated to the bottom. In many instances, although the bed of 

 dolomite is now at this place near twenty feet thick, some of the bones 

 were found even resting upon the carboniferous limestone itself, and 

 by careful selection would represent fossils occurring in the last-named 

 formation." 



The authors next describe the various bones which had been col- 

 lected : as the right half of a lower jaw with teeth ; an ulna ; a ra- 

 dius ; a metatarsal bone ; an ungual phalange ; two left ilia ; an is- 

 chium ; a left femur ; caudal vertebrae ; and discuss seriatim their rela- 

 tions to existing and extinct forms of Saurians. 



rate on Durdham Down, near Bristol ; by Henry Riley, M.D., and Mr. Samuel Stiitch- 

 bury." In the above-mentioned memoir the authors have established two new ge- 

 nera : 1st, Palaosaurus, of which tliey describe two species, P. cylindrodon, and P. 

 platyodon; 2nd, The codojitosaiu-us, the siiccies of which they had not designated. 



