REPLACED BY CARNIVOROUS TRACHELIPODS. 301 
different order of carnivorous creatures, destined 
to perform in another manner, the office which 
the inhabitants of Ammonites and various extinct 
genera of chambered shells then ceased to dis- 
charge. From that time onwards, we have evi- 
dence of the abundance of carnivorous Trache- 
lipods, and we see good reason to adopt the 
conclusion of Mr. Dillwyn, that " in the forma- 
tions above the Chalk, the vast and sudden 
decrease of one predaceous tribe has been pro- 
vided for by the creation of many new genera, 
and species, possessed of similar appetencies, and 
yet formed for obtaining their prey by habits en- 
tirely different from those of the Cephalopods."* 
The design of the Creator seems at all times 
to have been, to fill the waters of the seas, 
and cover the surface of the earth with the 
greatest possible amount of organized beings 
enjoying life ; and the same expedient of adapting 
the vegetable kingdom to become the basis of the 
life of animals, and of multiplying largely the 
amount of animal existence by the addition of 
Carnivora to the Herbivora, appears to have 
prevailed from the first commencement of or- 
ganic life unto the present hour.* 
* Mr. Dillwyn observes further, that all the herbivorous marine 
Trachelipods of the Transition and Secondary strata were fur- 
nished with an operculum, as if to protect them against the 
carnivorous Cephalopods which then prevailed abundantly; but 
that in the Tertiary formations, numerous herbivorous genera 
appear, v*hich are not furnished with opercula, as if no longer 
recjuiring the protection of such u shield, after the extinction 
