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genera in those shells with plain septa, one spiral (Nautilus), and 
another partly straight and partly spiral, ( Spirula ) ; so, of these 
shells with sinuous septa, we have the spiral (Ammonites ) , and the 
partly straight and partly bent, which have not been yet noticed, and 
which I shall venture to place under the following genus. 
LXXIX. Hamites. A multilocular hook-formed shell, with sinuous 
septa, with no evident siphunculus. 
The uniform figure of these fossil shells sufficiently separate them 
from every other genus ; and undoubtedly this separation would have 
been made long before this, if sufficient attention had been paid to 
the real forms which the fragments of this fossil possessed ; and if a 
sufficient number had been obtained to have allowed the making of 
the necessary comparison. 
One circumstance has particularly tended to mislead those who may 
have been induced to make any inquiries on this subject. All the casts 
of the fossils of this genus which I have met with, except one in sand- 
stone from Wiltshire, are formed of a pyritous clay, which, when the 
shell has been entirely removed, so readily gives the idea of having 
been in a soft state, that the hooked form of the specimens have been 
attributed to their having been bent and distorted whilst in that state. 
Such an idea might even be readily excited by the specimen, Plate X. 
Fig. 5, found in the stratum of green sand in Wiltshire. Plate X. Fig. 
2, shows a specimen, in which the first approximation to the hooked 
form is observable. Plate X. Fig. 4, represents a specimen, in which 
the turn of the hook is completely made ; and evidently in such a direc- 
tion, as could not have allowed of the formation of a spiral turn. In 
this specimen, enough of the smaller end of the fossil is left to show, 
that it was continued in a straight direction from the bend. This, it 
may be observed, is the termination in which alone we could have 
expected the spiral turn ; but which, going off in a straight line after 
the bend, determines the hooked form to belong to this fossil. 
The specimen Plate X. Fig. 3, which I purchased from the Le- 
