452 
OBSERVATIONS ON THE ANIMALS INHABITING 
MULTILOCULAR SHELLS, 
CHIEFLY WITH A VIEW TO THE GEOLOGICAL IMPORTANCE OF THE SUBJECT, 
By D. T. Anstep, Esq. M.A. F.G.S. F.C.P.S. 
OF JESUS COLLEGE, CAMBRIDGE.* 
In two former papers on this subject, I have endeavoured to give 
a somewhat popular account of cephalopodous animals and their 
shells, when the shells so far resemble those of the Nautilus and 
Ammonite as to be referrible to them as types: in other words, 
when the shell is divided into a limited number of compartments, 
the walls of separation being formed according to a constant law, 
and communicating by an aperture always retaining its relative po- 
sition. It remains now to consider two cases departing from these 
types: one of them is the family of Belemno-sepia, in which the 
concamerated structure appears to have been of somewhat inferior 
importance, and is found only in a small portion of the shell; the 
other is D’Orbigny’s family of Foraminifera, and is characterized 
by the peculiar and varied forms of the chambers, which communi- 
cate only by small, irregularly-placed apertures, bearing no relation 
to, and not having the same use as, the regular opening for the si- 
phuncle in the Ammoneata and Nautilacea. 
Although the species of Belemno-sepia are tolerably numerous, 
and the specimens very abundant, yet all of them belong to the 
same genus ; and we may at once proceed to consider the nature of 
the shell and other parts found fossil, and then, as in the Siphoni- 
fera, trace from analogy the probable habits of the former possessor, 
and its connection with, and bearing upon, the other genera of 
Cephalopoda. 
As it is usually met with, the Belemnite is of a more or less cy- 
lindrical form, but always coming to a point at one end, and some- 
times swelling out at the other, and presenting a funnel-shaped 
aperture, in which is often contained a series of concayo-convex 
plates, greatly resembling in appearance a pile of watch glasses 
heaped upon each other, every one smaller than those below it, and 
rising into a cone. Such is the appearance of the fossil, we say, as 
it is usually found ; but it is very necessary to consider how far 
* Concluded from page 284 of the last number. 
