146 Proceedings of the 



derangement of the beds, these masses appear to have intro- 

 duced themselves from below, and been developed there. Ma- 

 rine salt is also found in these earths ; and M. Dufresnoy supposes 

 that the famous bed of sea salt at Cardonne in Catalonia ought to 

 be classed among the chalk beds. But it is in the zoological 

 characteristics of these formations of the south of France that M. 

 Dufresnoy has found the most distinct proofs of his theory, and, at 

 the same time, the most remarkable anomalies. M. Dufresnoy, in 

 addition to the belemnites, ammonites, and other fossils peculiar to 

 chalk, has found in these earths the bulla, the cypraea, the melonia 

 several kinds of the Venus, the Lucina, the crassatella tumida, 

 the neutina perversa, and other fossils, which had hitherto been 

 only found in the terrains tertiaires. This would, at first sight, 

 appear to materially lessen the reliance to be placed on the zoolo- 

 gical characteristics of strata ; but it must be considered that, in 

 judging of the character of a stratum from its zoological character- 

 istics, there are four points to be specially examined. 1. The minute 

 difference of the species of fossils. 2. The geographical position of 

 the bed : this is important, because it is to be supposed that a 

 difference of latitude produced the same difference in zoological pro- 

 ductions of the ancient as of the modern world. 3. The position 

 of the different species in the strata. 4. The relative number of 

 the species, which are characteristics of the stratum in ques- 

 tion, and of those of which the geognostic position appears an 

 anomaly. 



In the present case, M. Dufresnoy informs us that the anomalous 

 or littoral fossils (by which we mean those usually found in the 

 terrains tertiaires) are assembled in layers distinct from those which 

 contain the pelagian fossils (as we may call those fossils which 

 are characteristic of chalk), and appear the results of a separate 

 deposit. We might thence be led to suppose that, while a precipi- 

 tate of chalky limestone, enveloping the belemnites, ammonites, and 

 other pelagian fossils, was forming at the bottom of the deep seas, 

 a calcareous earth, enveloping the cerites, the ampullae, and other 

 molluscae which could inhabit shallow waters, was simultaneously 

 forming itself near the shores, and in the shallow waters ; so that 

 the chalk and the terrains tertiaires would, according to this 

 hypothesis, have been formed nearly at the same time, and in the 

 same seas, but at different depths. Thus the fossils similar to, 

 though rarely identical with, those of the terrains tertiaires, would be 

 the littoral fossils of the seas at the epoch of the formation of the 

 chalk. This would throw light on the nature of the chalk of 

 Maestricht, which is so different from all others, and might be 

 supported by the presence, in that bed, of the metosaurus, an 

 animal which, if a marine animal at all, could only have lived near 

 the shores. But the concurring observations of different kinds, 

 establishing that the chalk deposits and the terrains tertiaires belong 

 to two distinct and probably remote epochs, are too numerous to 

 admit of our adopting the above hypothesis. As, however, the co- 



