322 PROF. EHRENBERG ON ANIMALS OF THE CHALK 
place the form has been nowhere observed with certainty in the 
chalk, which is likewise the opinion of Bronn in the Lethea Geo- 
gnostica, ii. p. 1135, 1838 ; and, secondly, it is uncertain whether 
the so-called living form was not merely a particle of sea-sand as 
old as the arenaceous beds of the calcaire grossier of Paris, since 
the observer has recognised and described none of the characters 
of the living animal, and wherever chalk cliffs are situated near 
the sea, shells of chalk animals are found detached in the sand. 
Nothing can therefore be concluded from this form, especially 
as the living animal from the Red Sea, which, under the name 
of Coscinospira Hemprichii, I have placed in quite a different 
family of Polythalamia*, likewise very much resembles exter- 
nally the Paris fossil species. 
A far more important investigation of recent animals occurring 
in the chalk was published by Leopold von Buch in 1834, to 
which, however, attention has not hitherto been paid in geolo- 
gical compilations. It relates to some species of the genus 
Terebratula. M. von Buch, in his critical classification of this 
genus of shells so abundant in forms and of such geological 
importance, published in 1835 in the Transactions of the Aca- 
demy for the year 1833, p. 45+, observes, “ Nevertheless there 
is no (living) species of this section (Loricata) which could be 
considered as perfectly identical with fossil species ; moreover, 
this perfect identity is limited, even to the present day, to but 
very few species, perhaps merely to two or three. Terebratula 
vitrea is not rare in the chalk ; and Ter. striatula, of Mantell and 
Sowerby, which occurs in the chalk and upper Jura beds, differs 
but little from the well-known Ter. caput serpentis.” In this 
representation, it is positively asserted of Ter. vitrea only that it 
is a living form of chalk animals; and he who sees and exa- 
mines the specimen upon which this conclusion is based, as I 
have done, will be able to pronounce no other opinion. Now, 
although an identity has been here recognised and can be safely 
asserted, yet there exists an element of embarrassment as regards 
important conclusions in the great variety of form in the species 
of this genus, which, from a chaos of names hitherto destitute 
of any certain limitation, had, by that difficult but important 
* «On the formation of the chalk and the chalk marl out of invisible organ- 
isms ;’ in the Transactions of the Berlin Academy for 1838, published in 1839, 
p- 120. pl. i., and p. 131. pl. ii. fig. 2. 
+ In the separate edition on Yerebratule, which was published in 1834, 
itis p. 25. 
