198 
X^UTILCIDEA. 
1873. Kautiliis truncatuti, Colleiiot, Description G^ologique de I’Anxois, 
p. 292. 
1882. Nautilus Etheridge, Quart. Joiirn. Geol. Soc. (Proceed- 
ings — Aiinhersary Address), vol. xxxviii. p. 171. 
1889. Nautilus tnincatus, Wilson and Crick, Geological Magazine, New 
Series, dec. iii. toI. vi. no. viii. p. 341. 
Sp. Char. “ Thick, flattened, plain, iimbilicate ; back flat, mouth 
elongated, four-angled ; siphuucle nearest to the inner margin of the 
septum.” {Sowerhy.) 
Remarics. The shell in this species is somewhat compressed on the 
sides, and the periphery is broadly truncated, the aperture higher 
than wide ; the umbilicus with a very small opening \ The surface 
of the test is marked only with lines of growth. The septa are ap- 
proximate and slightly flexuous on the sides, nearly straight in 
crossing the periphery. The siphuncle is situated below the 
centre. 
This species is most nearly allied to N. he.vayoyius, J. de C. 
Sowerby : but the latter is distinctly umbilicated with the sides of ; 
the umbilicus very steep, it l^s also wider and more flexuous septa. | 
These two species agree, however, in having a narrow flattened i 
periphery, and a siphuncle situated below the centre. | 
Besides 8owerby’s original type of X truncatns, there are in the 
Museum (‘ Sowerby Collection ’) two specimens from the Lias of I 
Kilsby Tunnel, Northamptonshire, -which are referred to that species I 
with some doubt, owing to their imperfect condition. They are | 
numbered 19518 I and 19518 m ; they both have a larger umbilicus | 
than Sowerby’s type, and in this respect approach N. hexagonus. f 
M. Eudes-Deslongchamps, in ‘ Etudes sur les Etages Jurassiques [ 
Inferieures de la Normandie ’ (1864, p. 149), cites Nautilus hexa- IJ 
gonus as occurring in the Great Oolite (Assises superieurs, Calc, k j 
polyp.) of Ranville, -nEich is probably a mistake, us there are two i 
specimens in the British Museum from the same locality and horizon, j 
which are undoubtedly N. tnincatus ; and as M. Deslongchamps | 
mentions only one species of Nautilus at Kanville, it is most likely j 
to have been the last-named speeies. L 
A large specimen (registered No. 34297) from the Upper Lias of i 
Milhau (Aveyron), Erance, is also referred to the present species jl 
with some hesitation, as the characters are not fully ascertainable. 1 1 
The shell is apparently full-grown ; the test is preserved on one side 
of it and exhibits strong lines of growth ; the deep sinus of the 
^ D’Orbigny represents it (he. cit. pi. xxix.) as quite closed, but this is an 
error. 
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