STILL FOUND IN A LIVING STATE. 351 
deposit itself*. An accurate distinction of the Terebratule ac- 
cording to characters defining precisely their species, had then 
however not been attempted. Moreover, Defrance merely as- 
serted the Terebratula vitrea of the chalk to be identical (paroit 
étre identique) with the recent species, and with regard to T’ro- 
chus and the other species, merely observed that, notwithstanding 
the great extent of his collection of fossils, they were the only 
ones occurring in and below the chalk with which he had be- 
come acquainted analogous to organisms still existing (qui oni de 
Panalogie avec des espéces qui vivent aujourd’ hui). 
Especially remarkable therefore were the cotemporaneous ob- 
servations of Dr. Fitton, who made known several recent river- 
shells, especially Paludina vivipara (= Vivipara fluviorum, Pa- 
ludina fluwviorum), as occurring in great masses and entire beds 
in the Isle of Wight, in the stratum situated as supposed be- 
neath the chalk, and which the English call Wealden clay after 
the Weald (Forest) of Sussex, where it likewise occurs +t. 
In the subsequent important works of Deshayes and Lyell, 
all these observations, after an exceedingly careful revision 
of fossil phenomena in the years 1831 and 1833, were charac- 
terized as uncertain and erroneous; and 0: the contrary, the al- 
ready mentioned doctrine was asserted, that in the tertiary strata 
only of the earth’s crust were still living forms with certainty to 
be found. Friedrich Hoffmann also, in his lectures of 1834 on 
the history of Geognosy, when speaking of the Weald clay and 
Dr. Fitton’s observation of recent fresh-water shells in it, says, 
“there appears, however, to be some error heret.” 
Thus then the cautiously advanced opinion of Von Buch, re- 
newed in 1834, upon the identity of Terebratula vitrea of the 
chalk and that of the present world, became of fresh and espe- 
cial importance, although it has also hitherto been disregarded 
in most recent works on the subject, from the predominant in- 
clination in favour of Lyell’s Eocene period; and the subsequent 
labours of Milne Edwards § and Agassiz have attacked it in other 
directions. Let the following catalogue then awaken further 
interest in these inquiries. 
From 1824 the following fourteen forms have been noted as 
* Tableau des corps organisés fossiles, par M. Defrance. Paris, 1824, p. 63. 
+ Fitton in Thompson’s ‘ Annals of Philosophy,’ 1824, vol. viii. p. 374. 
t F. Hoffinann’s Geschichte der Geognosie, Berlin, 1838, p. 239. 
§ Annales des Sciences Naturelles, 1836, vol. vi. p. 321. 
