196 
XACTTILOIDEA. 
Remarlcs. “ This species resembles Nautilus striatus, J. So'werby \ 
in its general form and perfectly in its sculpture, but it is distin- 
guished by its completely closed umbilicus. A large but imperfect 
and crushed example (No. 39850) represents the adult stage in the 
growth of the shell, while the young is exemplified in an exquisitely 
preserved specimen (No. 39887). The name simillimus which we 
have given to this species is intended to express its close resem- 
lance to N. striatus.” {Foorcl and G. C. Crick.) 
Horizon. Lias. 
Locality. Charmouth, Dorsetshire. 
Well represented in the Collection. 
Nautilus Araris, Dumortier. 
1869. Nautilus Araris, Dumortier, Ltudes Paldontologiques du Bassin 
du Rhone, pt. hi. p. 56, pis. vi., vii. 
1876. Nautilus Araris, Blake, in Tate and Blake’s ‘The Yorkshire 
Lias,’ pt. ii. p. 312. 
1884. Nautilus Araris, Simpson, The Fossils of the Yorkshire Lias, 
2nd ed. p. 60. 
Bp. Char. Shell large, discoid, compressed, widely umbilicated ; 
composed of two or three whorls which are much higher than wide, 
rounded in the umbilical region with a slightly flattened periphery. 
Siphuncle very large, situated below the centre. Umbilicus large 
with slightly rounded borders, exposing the two inner whorls, the 
outer whorl covering them to the extent of rather more than half 
their width. There are from twenty-two to twenty-four septa, 
which are strongly curved on the sides, and bent backwards towards 
the umbilicus in a very remarkable way. Surface ornamented with 
interlacing lines, forming a network of which the lougitudinal lines 
predominate. The shell must have attained a very great size, a 
specimen measuring 210 millim. in diameter consisting entirely of 
the septate portion, without any sign of the body-chamber. 
Remarks. Nautilus Araris is separated from all other Liassic 
species by the height of the whorls, the size of the umbilicus, the 
peculiar curvature of the sutures, and the large size of its siphuncle. 
It is said by Dumortier to be characteristic of the zone of Belemnites 
elavatus. Professor Blake ^ records it from Robin Hood’s Bay in 
the zone of Ammonites armatus. 
This species is admirably represented in the Collection by several 
1 Min. Conch, vol. ii. p. 183, pi. clxxxii. 
^ Tate and Blake’s ‘ The Yorkshire Lias,’ 1876, pt. ii. p. 312. 
