FACTS AND INFERENCES. 29& 



great reason to believe, that the nuclei of many of our lias and iron- 

 stone nodules, which contain the best preserved petrifactions, original- 

 ly consisted of such matter. Besides, when we find in the same bed, 

 shells that are well preserved, associated with others that have been 

 violently broken, distorted, or mutilated, what can we think, but that 

 incidental circumstances have preserved the former, from the violence 

 that injured the latter? It is well known, that very entire shells are 

 found even in gravel beds, where they might be expected to be 

 broken or water-worn. 



After all, what can be meant by the assertion, that the shell-fish 

 have lived and died on the spot? Can it mean, in regard to such 

 beds as our alum shale or oolite, that the animals imbedded actually 

 lived in the clay or calcareous matter? That is physically impossible. 

 Pholades, or similar shell-fish, might burrow in beds of clay or marl; 

 but that is not the state in which our petrified shells are found, and 

 we rarely meet with shells of that description. The stone in which 

 the mytilus lithopkagus occurs, is very different from the oolite in 

 which it is found, and may be presumed to have been transported 

 from a distance. Does the assertion mean, that the shell-fish lived 

 on the surface of the stratum below, and were covered by the de- 

 position of the clay or calcareous matter over them? Had that been 

 the case, we should have found the mass of shells at the bottom of 

 the beds that overwhelmed them. Does it mean, that the animals 

 lived on the surface of these beds, and were covered up by the 

 succeeding beds? Then we should have seen them all in the upper 

 part of the clay or oolite. Or, does it mean, that these beds, particu- 

 larly the limestone beds, were formed by the calcareous matter 

 i-esulting from the decay of successive generations of shells? In that 

 case, we ought to find the entire shells only in the upper part of the 

 beds, and the lower parts should consist of nothing but lime, or of 

 finely comminuted particles of shells; whereas we see the shells and 



