282 Antediluvian Zoology and Botany, 



may still be traced at intervals, and sparingly, in subjacent beds. 

 In the beds succeeding the chalk, we have a remarkable excep- 

 tion. At no point is there a more strongly marked change than 

 is exhibited at the termination of this formation. The clays 

 which follow are peopled by a multitude of animals differing 

 essentially from all that had preceded them : an entirely new 

 series, '' not formed," as Mr. Parkinson observes, " by the 

 gliding of one genus into another, or by changes induced in 

 the structure of the animals, but, as far as the state of our 

 knowledge will allow us to judge, by a new creation, adapted 

 to. the especial purposes which Providence had destined to 

 accomplish." 



One of the most remarkable facts elicited is, that certain Tes- 

 tacea, whose genera were abundantly preserved and prolonged 

 through so many formations, should now exist so sparingly, or 

 be entirely lost. We might instance the Terebratulae, which 

 abound no less in the mountain limestone than in the chalk, and 

 in almost every intermediate rock, which are absent in nearly 

 every one of our tertiary beds, and reappear. in the most recent. 

 Not less than 100 fossil species of Terebratulae, and myriads 

 of individuals, are known to us ; but the recent shells of this 

 genus are comparatively few. Of Trigonia, also, 25 species 

 are found in our strata, often abundantly, and terminating, 

 like the Ammonites, with the chalk. Until lately, this genus 

 was considered to be extinct ; but one species has been dis- 

 covered on the shores of New Holland. Of Ammonites, so 

 profusely distributed, whose species amount, it is said, to no 

 less than 200, and of which about 175 are known in the 

 English formations, none now remain. 29 species of Pro- 

 ducta, 3 of Pentamerus, and 19 of Spirifer, inhabited the 

 waters that produced the transition and mountain limestone, 

 and contiguous shales ; but these genera are altogether ex- 

 tinct. Indeed, almost the whole series of antediluvian multi- 

 locular shells seem to have shared a similar fate. 



On the other hand, instances are no less abundant and 

 striking, where the recent species comprehended under certain 

 genera do greatly outnumber the fossils. Thus, under the 

 Linnean genus Conus are comprised 155 species existing; but 

 only 3 occur fossil in our London clay. The genus Cypr^^^a 

 contains about 110 living species, and only 4 fossil in the ter- 

 tiary beds. 



Thus, during the revolutions of ages, some races have 

 been extinguished, and have given place to others which may 

 still be traced in our seas. In the great tertiary deposits of 

 the Sub- Apennines, Brocchi conceived he could point out some 

 marine shells, which are now very widely dispersed, in the 



