Intelligence and Miscellaneous Articles. 151 



portion of 1 to 7 j but the complicated species, in the same divisions, 

 are in the reverse ratio nearly of 17 to 1. 



On comparing the proportions which the classes of shells under 

 each division bear to each other, differences equally remarkable are 

 observable. Thus the univalves in the first division are to the com- 

 plex species as 1 to 4 j in the second, as 1 to Hrd only ; and in the 

 third, as 32 to 1. 



The ancient formations are characterized by complicated shells, the 

 middle series by bivalves, and the upper by simple univalves. 



Mr. Taylor next illustrates from the Tables, Mr. Dillwyn's remarks 

 on the distribution of carnivorous and herbivorous Trachelipodes. He 

 shows that, in the English formations, the Zoophages comprise 22 

 genera, and 171 species. They may be considered as appertaining 

 to, if not as wholly characteristic of the tertiary formations ; and 

 many of the genera are continued in our present seas. Of the Phyl' 

 liphages, 22 genera and 1 G8 species are distributed through the se- 

 condary and tertiary formations. 



When the members of each of these classes are arranged according 

 to the three geological divisions already mentioned, we find that the 

 turbinated univalves of the older strata or rocks belong almost en- 

 tirely to the herbivorous family, 12 genera having originated there, 

 which have been perpetuated through all the successive strata, and 

 still inhabit our waters ; that in the middle series of formations, this 

 preponderance of animals possessing similar habits was preserved ; 

 and that, in the last series, after the chalk was deposited, this order 

 was suddenly reversed, in the proportion of 5 to 19. 



Mr. Dillwyn observed that all the marine Trachelipodes, of the 

 herbivorous tribes, in the ancient strata, are furnished with an oper- 

 culum, seemingly intended as a protection against the Cephalopodes, 

 or carnivorous order of Nautili, Ammonites, &c., which, at that time, 

 abounded in the seas. After the epoch of the extinction of this order 

 (which terminated chiefly with the chalk), numerous unoperculated 

 genera appear, as if no longer requiring such a shield to protect them 

 from an extinct enemy. As carnivorous turbinated univalves were 

 almost entirely absent from the strata which contained the Ammo- 

 nites, the Nautilidise, and the Belemnites, so the extinction of these 

 immensely numerous tribes, being also carnivorous, or predaceous, 

 was counterbalanced by the creation of a multitude of new genera, 

 possessed of similar appetences. 



Recurring again to our table for illustration of these positions, we 

 observe that only 3 genera and 18 species of carnivorous turbinated 

 univalves were coeval with the Cephalopodes, comprising 200 species, 

 in the secondary formations ; but that tlie same strata contained 17 

 genera and 87 species of Fliyiliphages. 



When the Cephaloi)odos ceased with the chalk, at the same time 

 with the numerous families of fossil Echinidia;, the Trigoniae, and 

 nearly all the Tcrrebratula;, they were replaced by 19 genera and 

 1 j3 new s|)eciuH of Zoophages. 



On comparing the existing classes of shells with correspond- 

 ing 



