INHABITING MULTILOCULAR SHELLS. 45 
existed. What the exact mode of increase in a shell like this may - 
have been, and whether any principal organ of the body was imme- 
diately connected with the chambers, the present state of our know- 
ledge with regard to this animal does not allow to be determined. 
It is to be hoped that some one of our numerous scientific navigators 
may follow the example of Mr. Bennett,* and, by preserving and 
putting into the hands of a naturalist the animal of a Spirula, set 
them and many other questions at rest for ever. 
It is a matter of extreme difficulty to determine whether the Or- 
thoceratite was an external or internal shell. Dr. Buckland has con- 
sidered the latter as the most probable opinion ; but, from the very 
large size of the last chamber, and the difficulty of conceiving so 
enormous a cephalopodous animal as to require an internal shell three 
feet long, we may be allowed to doubt the correctness of such an as- 
sumption. The siphuncle, too, varies so much, and was evidently so 
very important an organ in this genus, that we hardly know how to 
bring our analogies to bear in the consideration of it. If this singu- 
lar shell was really the mere skeleton of an animal whose predaceous 
habits were at all proportioned to its size, we must pause with wonder 
and astonishment at the state of animal life in those seas which could 
support myriads of these giant molluscs upon the exuberance of its 
stores. 
There is one more question which presents itself with regard to this 
part of the subject, although it applies equally to other parts; and 
that is, whether the temperature required for the developement of 
these large animals in such amazing numbers was greater than is at 
present known in the climates where they are found. Many, indeed 
most, of the beds remarkably abundant in these fossils, are in high 
northern latitudes ; and it has been imagined that a low temperature 
is not favourable to such extreme vitality. It may be so, but we are 
not justified in concluding at once that it must be so. Probably in 
no part of the tropical seas is there so much living matter as in an 
equal area in the Polar seas; and it is a well-known fact that the 
Whale has but to swim for a short space with its mouth open in oy 
der to satisfy its appetite, which in so huge a creature must necessa- 
rily require a large quantity of food. Still, as many other known 
facts concerning these early seas seem to point more or less to the 
* It is to the fortunate capture of an individual of the Nautilus Pompilius 
by this’ gentleman that we are indebted for the valuable memoir of Mr. 
Owen, which has thrown so much light on the subject of the cephalopodous 
animals of multilocular shells. 
