American Association. 281 



SUCCESSION OF FOSSILS IN BRITISH ROCKS. 



Prof. Kamsay presented an elaborate paper on the succession of 

 fife in British rocks, illustrated by a diagram exhibiting the num- 

 ber of species and genera of fossils in each formation, and the 

 number common to each pair of successive formations. The sub- 

 ject is a large one, even in the facts relating to a single limited 

 area. It is still more difficult if we attempt to extend our 

 view to the world ; and in reasoning on the facts attained, 

 defects in the data appear at every step. Above all we are as yet 

 quite uncertain as to the relative value in point of time of geolo- 

 gical formations, or of the intervals which may separate them, 

 nor do we know the proportion of species lost and preserved in 

 any one epoch. Prof. Ramsay, however, took a firm hold of his 

 subject, and pointed out some very remarkable facts indicated by 

 his comparisons of British formations. 



" Professor Ramsay said the subject to which he intended to 

 direct the attention of the Association was one which had 

 necessarily engaged the attention of Geologists ever since it be- 

 came an established fact that there was such a thing as order in 

 the superposition of strata, each formation being characterised by 

 its peculiar suite of organic remains. It was found that genera 

 and species had long succession, and had several times been ex- 

 tinct on the face of the earth. It was an easy way of accounting 

 for this to suppose that each great extinction was marked by 

 some great catastrophe which swept all clean from the face of the 

 earth, and then there was a new creation. Few geologists now 

 believed this, and some assert that as one species died out another 

 was created, so that had we all the links perfect there wouktbe 

 found a gradual dovetailing — a perfect passage of one formation 

 into the other. The diagram before them he had constructed to 

 aid himself in investigating this subject. It was constructed 

 purely with reference to the formations in the British islands, and 

 the various fossils found in these various formations. But the 

 same general laws would be found to obtain, in a modified manner, 

 in other localities. The first division in the diagram is the Slandeilo 

 flags, where we have the first development of organic life. In these 

 we have twenty species and fifteen genera. Eight of these are 

 trilobites. Apparently the succeeding Lower Silurian rocks rest- 

 ed upon them with perfect conformity. There is no appearance 

 of a break in the series ; yet we find only find five genera and 

 one species pass into the next strata. "What was the reason 



F 



