CLASS CEPHALOPODA. 15 
nal furrow, or by two or more furrows towards the summit, or, 
finally, as that surface is smooth and without furrows. 
Bodies very similar to the Belemnites, but without a cavity, 
and with rather a prominent base, form the genus ACTINO- 
CAMAX of Miller. It is also upon conjecture of a similar 
nature that reposes the classification of the 
AMMONITES, brug., 
Or the Cornua-ammonis, for they no longer exist, except 
among fossils. They are distinguished from the nautili by 
their septa, which, instead of being plane or simply concave, 
are angular, and sometimes undulated, but most frequently 
crimped on the edge like the leaf of an acanthus. The small- 
ness of their last cell seems to indicate that, like the spirula, 
they were internal shells. They are very abundant in the 
strata of secondary mountains, where they are found varying 
from the size of a lentil to that of a coach-wheel. ‘Their sub- 
divisions are based upon the variation of their volutes and 
siphons. 
The name of AMMONITES, Zam. (SIMPLEGADES, Montf., 
82), is particularly restricted to those species in which all the 
whorls are visible. Their siphon is near the margin. 
They have lately been divided into the AMMONITES, 
Planites of Haan, where the edge of the septa is foliaceous, 
and into the CERATITES of Haan, where it is simply angular 
and undulated. 
Those in which the last whorl envelopes all the others form 
the ORBITULITES, Lam., or the GLOBITES and the GonIA- 
LITES of Haan, or the PELAGUSES, Montf. 62, in all of 
which the siphon is situated as in the preceding ones. 
The. ScAPHITES, Sowerb., are those in which the whorls 
are contiguous and in the same plane, the last one excepted, 
which is detached, and reflexed on itself. 
Some, BACULITES, Lam., are entirely straight, without any 
