30 
two living crinoids are known in the deep waters in some parts 
of the Indian and Australian seas, hut they belong to a 
different family, one which although represented by only a few 
species, has come down to our period continously from the 
Liassic age. The remarkable point of the discovery is that 
there now exists, living at great depths, a representative of a 
family which has dwindled away, and to all appearances 
become almost extinct, before the formation of the older 
tertiaries. It is moreover eminently suggestive, and led 
naturalists, in connection with other circumstances and im¬ 
proved mechanical appliances, to pay increased attention to 
deep sea dredging. 
The results of several expeditions organised for this purpose 
are as curious as unexpected, and have in some respects entirely 
altered the views of naturalists in regard to life in the depths 
of the ocean, and have established in a remarkable manner the 
close resemblance of the conditions under which the chalk beds 
were deposited and those existing at the bottom of the ocean along 
the tract of the Gulf stream at the present day. The general 
conclusion arrived at is, that chalk of the cretaceous period is 
now in the process of formation at the bottom of the Atlantic. 
Dr. Carpenter goes even further than this, and regards it as 
highly probable that the deposit of Globigerina mud has been 
going on over some part or other of the North Atlantic sea-bed 
from the cretaceous epoch to the present time, (as there is 
much reason to think that it did in anterior geological periods), 
this mud being not merely a chalk formation, but the con¬ 
tinuation of the chalk formation; so that we may be said to 
be still living in the cretaceous period.” 
It is to some of the points of evidence in this direction that 
I wish to confine my remarks. The simple deposit of car¬ 
bonate of lime has no geological importance, for it is found in 
beds of all ages, but the peculiar lithological characters of the 
chalk demand attention. Chalk is a carbonate of lime made 
up of the decomposition of Testacea, Echini, Corals, &c., and 
chiefiy of the shells of certain Foraminifera, the Globigerina 
and Textularia occasionally entire, but generally showing them¬ 
selves in the form of more or less detached or broken cells. 
