Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/257

which they are found, and vary in size from a line to more than four feet in diameter.^[1]

It is needless here to speculate either on the physical, or final causes which produced these curious changes of species, in this highest order of the Molluscous inhabitants of the seas, during some of the early and the middle ages of geological chronology; but the exquisite symmetry, beauty, and minute delicacy of structure, that pervade each variation of contrivance throughout several hundred species, leave no room to doubt the exercise of Design and Intelligence in their construction; although we cannot always

SUB-GENERA OF AMMONITES.
LIVING SPECIES	Gonia- tites	Cera- tites	Arie- tes	Falci- feri	Amal- thei	Capri- corni	Planu- lati	Dor- sati	Coro- narii	Macro- cephali	Armati	Den- tati	Ornati	Fle- xuosi
In Tertiary strata
In Cretaceous system				2	4					9	4	13	2	3
In Oolitic system				22	27	12	26	5	11	11	11	4	5	3
In Saliferous system		3	12
In Carboniferous system	7
[nested 1]In Primary strata	17
Total 223 species.

"It is easy to see how important, in questions concerning the relative antiquity of stratified rocks, is a knowledge of Ammonites, since whole sections of them are characteristic of certain systems of rocks."—Phillips's Guide to Geology, 8vo. 1834, sec. 82.

1. Mr. Sowerby (Min. Conch. vol. iv. p. 79 and p. 81,) and Mr. Mantell speak of Ammonites in Chalk, having a diameter of three feet. Sir T. Harvey, and Mr. Keith Milnes, have recently measured Ammonites in the Chalk near Margate, which exceeded four feet in diameter; and this in cases where the diameter can have been in a very small degree enlarged by pressure.

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1. The strata here termed primary are those which, in the Section, (Pl. 1,) I have included in the lower region of the transition series.