NAUTILIDJE. 
201 
cated, the umbilicus small, exposing the inner whorls. Aperture 
elongated, much higher than wide. Septa approximate, the sutures 
gently curved on the sides and forming a slight backwardly-directed 
sinus upon the periphery. Siphuncle nearly central, or very slightly 
above the centre. The surface of the test is smooth upon the sides 
of the shell, but striated longitudinally around the umbilicus and on 
the periphery. 
RemarTcs. This species may be distinguished from others when 
the test is absent by the approximate septa and very compressed 
form of the shell ; and when the test is preserved, the striae developed 
only on the periphery and in the umbilical region separate it from 
RaiUilus striatus and N. intermeclius. 
The example representing this sjmcies in the Collection agrees 
with d’Orbigny’s description and figures except in two respects : 
first, the form of the umbilicus, which has steep walls and an an- 
gular border in the British Museum specimen, whereas in d’Orbigny’s 
figure (pi. xxvi. fig. 1) the sides of the umbilicus are sloping and 
gently rounded ; secondly, the periphery in d’Orbigny’s specimen is 
flattened, in ours it is narrowly rounded. Our specimen is, how- 
ever, only half the size of d’Orbigny’s, and therefore the characters 
in w’hich the two differ may be accounted for by their disparity of age. 
Dumortier records this species from the lowest beds of the Middle 
Lias ; d’Orbigny from the Upper Lias, and always in association 
with Ammonites hifrons. 
Horizon. Upper Lias. 
Locality. Pontaine-Etoupe-Four (Calvados), France. 
Bepresented in the Collection by a single example. 
Nautilus Toarcensis, d’Orbigny. 
1842. Nautilus latidorsatus, d’Orbigny, Paleontologie Frau9aise (Ter- 
rains Jurassiques), vol. i. p. 147, pi. xxiv. {Not of Schlotheim.) 
1849. Nautilus latidorsatus, Quenstedt, Die Cephalopoden, p. 56. 
1849. Nautilus Toarcensis, d’Orbigny, Prodrome de Paleontologie Stra- 
tigraphique, vol. i. p. 245. 
1852. Nautilus latidorsatus, Giebel, Fauna der Vorwelt, Band iii. 
Abth. i. p. 153. 
1854. Nautilus Toarcensis, Millet, Paleontologie de Maine et Loire, 
p. 68. 
1857. Nautilus latidorsatus, Lycett, The Cotteswold Hills, p. 162. 
1858. Nautilus Toarcensis, Oppel, Die Juraformation Englands, Frank - 
reichs und des siidwestlichen Deutschlands, p. 241. 
