42 IMPERFECTION OF THE GEOLOGICAL RECORD 



1 



carbonaceous beds of the Trias, the fossil soils of the Portland 

 series, the estuarine Wealden beds would seem to be as favour- 

 ably situated as those of the coal formation for preserving land 

 shells, though possibly the flora of the Mesozoic was less suit- 

 able for feeding such creatures than that of the Coal period, 

 and they may consequently have become few and local. After 

 all, perhaps more diligent collecting and more numerous col- 

 lectors might succeed, and may succeed in the future, in filling 

 this and similar gaps. 



It is a great mistake to suppose that discoveries of this kind 

 are made by chance. It is only by the careful and painstaking 

 examination of much material that the gaps in the geological 

 record can be filled up, and I propose in the sequel of this 

 article to note a few instances, in a country where the range 

 of territory is altogether out of proportion to the number of 

 observers, and which have come within my own knowledge. 



It was not altogether by accident that Sir C. Lyell and the 

 writer discovered a few reptilian bones and a land snail in 

 breaking up portions of the material filling an erect Sigillaria 

 in the South Joggins coal measures. We were engaged in a 

 deliberate survey of the section, to ascertain as far as might 

 be the conditions of accumulation of coal, and one point 

 which occurred to us was to inquire as to the circumstances 

 of preservation of stumps of forest trees in an erect position, 

 to trace their roots into the soils on which they stood, and to 

 ascertain the circumstances in which they had been buried, 

 had decayed, and had been filled with mineral matter. It was 

 in questioning these erect trees on such subjects — and this not 

 without some digging and hammering — that we made the dis- 

 covery referred to. 



But we found such remains only in one tree, and they were 

 very imperfect, and indicated only two species of batrachians 

 and one land snail. There the discovery might have rested. 

 But I undertook to follow it up. In successive visits to the 



