XAUTILTDJ2. 
289 
by the sinuous form of the septal sutures and their much greater 
distance apart, and by the position of the siphuncle, which in 
d’Orbigny’s species is below the centre of the septa. 
This species, so far as is known, is confined to the Cambridge 
Greensand. 
Horizon. Cambridge Greensand. 
Locality. Xear Cambridge. 
Well represented in the Collection. 
[^Xautilus incec^ualis, J. Sowerby, Min. Conch, vol. i. 1813, p. 88, 
pi. xl. (lower figures). — This name was bestowed by Sowerby upon 
a young and imperfect individual alleged to have been derived from 
the Gault of Folkstone ; but it has all the appearance of a Cambridge 
Greensand fossil. It is a cast of the septate part of the shell, and 
has a maximum diameter of barely | of an inch. The umbilicus is very 
small, but it probably increased in size as the shell grew. Eleven 
septa are visible, the sutures of M'hich are slightly arched on the 
sides of the shell, but nearly straight in passing over the broad and 
somewhat flattened periphery. The sutures have an inner (dorsal) 
lobe, which was mistaken by 8owerby for the siphuncle, which he 
says is “ near the inner margin of the septum” ; it is not, however, 
visible, and therefore this specific character (an important one, when 
so few are available) is wanting. Upon this meagre material was 
Sowerby’s species based. 
Mr. Jukes-Browne ^ questions the identity of the Nautilus Clemen- 
linus of Pictet and Campiche with the N. Cleynentinus of d’Orbigny 
and remarks that both the figured forms appear to be represented 
among the Cambridge Nautili.^ the compressed forms agreeing with 
d’Orbigny’s species and the more inflated ones with Pictet and 
Campiche’s. Mr. Jukes-Browne thinks that the latter sufficiently 
agree with Sowerby’s N. incjequalis. If this were correct, the 
N. Clementinus of Pictet and Campiche would become a synonym 
of N. inaqualis of Sowerby. I should hesitate, for my own part, to 
accept this arrangement without seeing examples of Pictet and 
Campiche’s form. Though with abundant material before me, I 
find it impossible to determine wffiat maturer form, either of the 
’ “ Supplementary Notes on the Fauna of the Cambridge Greensand,” 
Quart Journ. Geol. Soc. vol.xxxiii. 1877, p. 489. 
^ Description des Fossiles des Environs de Sainte-Croix (Paleont. Suisse), 
ser. ii., pt. i. p. 144, pi. xix. ff. 1-5. 
^ Paleontologie Fran^aise (Terrains Cr^taces), vol. i. p. 77, pi. xiii. bis. 
PART II. V 
