106 
From the peculiar form of the chambers and septa in this fossil, an 
undulating or foliaceous suture is formed, which necessarily approxi- 
mates it to the genus Ammonites , and prevents our regarding any 
longer this simple suture as one of the generic characters of Nautilus. 
The siphunculus in the recent nautilus, I believe, always passes 
through nearly the middle of the septa. This is the case also with 
those nautilites of Shepey, which bear the general form of N. pom- 
pilius ; and with those found at Brentford, one of which, impregnated 
with pyrites, is represented Plate VII. Fig. 12. But in other speci- 
mens, as in the one just noticed, it passes much nearer to the inner 
part of the shell. In others, again, it passes nearer to the outer part 
of the shell ; and in one specimen which I possess, from Yeovil, 
Plate VII. Fig. 16, it is seen to run along the back of the shell. The 
septa, in these last specimens, frequently have an undulating direc- 
tion ; the fossil approximating, both in the situation of the siphuncle 
and form of the septa, to the Cornu ammonis. 
It should be remarked, with respect to the size of the siphunculus, 
that, independent of the difference which may perhaps take place in 
the degree of dilitation of the tube, at the time of its becoming in- 
volved in its matrix, considerable difference may result from the sec- 
tion of a specimen by which the tube is displayed. Thus, if the 
longitudinal section of the siphuncle is made directly along its middle, 
it will necessarily display a wider opening than if the section had been 
made more to either side. 
I am perfectly unacquainted with the nautilite without distinct 
chambers, or visible concamerations, mentioned under the article 
nautilite, by Bourguet, in his dictionary, on the authority of Spada, 
who describes it : “ Nautilites unius aufractus, dorso subrotundo, 
squameo, reliqua corporis parte palmata.” Spada, Cat. Lap. Agri 
V'eron. p. 20. I am also ignorant of the fossil which the inhabitants 
of Maltha call Capo di gatto ; and which Lhwydd describes as Nau- 
tilitce articulus, Lithoph. No. 303. I should, however, suppose it 
