194 
NAUTILOIDEA. 
Bemarlcs. The shell is thick-discoid, slightly compressed at the 
sides and flattened npon the periphery. The umbilicus is of mode- 
rate size and exposes the inner whorls. The siph uncle is situated 
a little above the centre. The septa are somewhat distant, and the 
sutures are slightly sinuated in crossing the periphery. The orna- 
ments consist of very distinct and regular longitudinal ridges which 
are crossed by a few irregular lines of growth. 
This species is distinguished from striataa by its squarish and 
more robust form and by the flattening of the periphery ; and from 
N. semistriatus by the former character, as well as by the superior 
size of the umbilicus, and the persistency of the ornaments of the 
test. From N. obesus, J. Sowerby, and N. truncatus, J. Sowerby, 
the present species may be distinguished by its open umbilicus. 
M. Chapuis ' has figured this species, or something very near to 
it, under the name N. aratm, var. (!, as previously noted ; but his 
figure, though agreeing in its ornamentation with Sower by ’s N. 
intermedins^ represents a more compressed shell with much closer 
septa. Such a form is met with in the Collection in the shape of a 
cast from Ilanden, near Schaffhausen, which has rather close septa, 
a narrow and very flat periphery, and somewhat flattened sides. It 
is questionable, however, whether this form can be regarded as 
identical with the N. intermedins of Sowerby, and the evidence 
which would connect it with Chapuis’s fossil is not quite complete, 
owing to the absence of the test. 
Another cast (No. C. 484), the locality of which is unknown, 
appears to belong to the same category as the one just described 
from Kanden ; it consists of the whole of the septate part of the 
shell, with the somewhat large open umbilicus characteristic of N. 
intermedins^ and agreeing in the flattening of the periphery and the 
somewhat flattened sides with the lianden fossil. 
A remarkably fine specimen (No. 39718) from Lyme Eegis may 
be referred provisionally to this species ; it is more inflated than 
the other examples, and the longitudinal ridges have a tendency to 
become obsolete on the sides. Its dimensions are as follows : — 
greatest diameter 9| inches, width of umbilicus 1| inch, width of 
aperture (a little distorted) 7 inches, height 4| inches. 
Horizon. Lias. 
Localities. British. Whitby, Yorkshire ; (?) Keynsham, Somerset- 
^ Fossiles des Terrains Secondaires de la Province de Luxembourg (Extr. du 
tom. xxxiii. des Mem. de I’Acad. Eoy. de Belgique), 1858, p. 11, pi. ii. 
ff. Ic, 1 d. 
