320 PROF. EHRENBERG ON ANIMALS OF THE CHALK 
Conchylia, the same phenomenon. With equal scientific accu- 
racy, also, have the recent researches of Milne Edwards on the 
genus Eschara led to the result, that not a single one of the 
numerous fossil species (27) of the oolite and chalk formation 
agrees with recent species; and the latest extensive and pro- 
found inquiries of Agassiz on fossil Fish and Echinites, have 
yielded a similar result *. 
Deshayes and Lyell subsequently collected these facts into 
systematic order; and the latter ingenious and experienced 
English geologist laid it down as a fundamental position, that 
according to the most accurate researches, neither in the transi- 
tion and oolite formation, nor in the chalk of the secondary for- 
mation, did remains exist of recent species; but that these first 
present themselves with the newer tertiary epoch of the earth’s 
formation. He therefore divided the tertiary epoch into four 
periods or times of deposition : 
the Eocene, 
or earliest dawning period of the present organic world, in whose 
strata very few recent species only have hitherto been found ; 
the Miocene, 
in which less than the half; 
the Older Pliocene, 
in which more than the half; and 
the Newer Pliocene, 
in which almost all the fossil remains agree with speciesy still 
living. 
This view has met with a very extensive reception, and has 
been echoed from many quarters; and the more so, from its 
adoption by Dr. Buckland in his widely diffused ‘ Bridgewater 
Treatise,’ 2nd edit. 1837. i. pp. 78, 79. It has acquired 
greater claims to favour, on account of the opinion having been 
also promulgated from other quarters, that our earth has been 
exposed at different periods to highly varied relations of tempe- 
rature; and, consequently, also to varied states of combina- 
* The only species of fish found both recent and fossii mentioned by Agassiz 
is Mallotus villosus of Cuvier. Alluding to the figure of it in his Recherches 
sur les Poissons Fossilles, Agassiz says, ‘‘ Les exemplaires contenus dans les 
géodes marneuses que l’on trouve sur les cdtes d'[slande, sont identiques avec 
les exemplaires vivans dans ces parages. On dit qu il se forme encore tous les 
jours de ces géodes. C’est le seul exemple que je connaisse de fossiles iden- 
tiques avec une espece vivante.”—Fech. sur les Poiss. Foss. feuilleton addi- 
tionnel, p. 116. 1838.—Ep. 
+ Lyell’s Geology, 4th edit. vol. iil. p. 808. German translation by Hart- 
mann, vol. iii. p. 42. 
