226 
NAUTILOIDEA. 
1884. Nautilus clausus, Mallada, Boletin de la Comision del Mapa Geo- 
logico de Espana, vol. xi., Sinopsis de las Especies Fosiles de 
Espana, p, 228 (p. 20 of the Sinopsis). 
1890. Nautilus clausus, Foord and G. C. Crick, Ann. & Mag. Nat. Hist, 
ser. 6, vol. v. p. 284, f. 14. 
S2^. Char. “ Shell inflated, rapidly enlarging, somewhat compressed 
on the sides, broad and flattened on the periphery ; surface of test 
smooth or marked only with very fine subregular lines of growth. 
Whorls completely involute, widest in the region of the umbilicus, 
which is closed by a shelly callus. Aperture much wider than 
high. Septa slightly curved on the sides and forming a shallow 
sinus on the periphery. Siphuncle a little below the centre. 
Remarks. “ This species bears some resemblance to Nautilus suh- 
truncatus, Morris and Lycett \ and it is also like N. Baheri of the 
same authors ; it differs from the former in its smooth test and 
from the latter in the same feature and also in its closed umbilicus. 
“ Fig. 50 was traced from a young specimen (2 inches in dia- 
meter) of this species from the Inferior Oolite of Caen, Normandy 
(No. 37024). The anterior boundary (a) of the impression of the 
shell-muscle can be distinctly followed from the umbilicus on the 
Fig. 50. 
one side across the periphery to the umbilicus on the other ; but no 
trace exists of the posterior boundary. The letter s represents the 
last septum. 
“ Figures 46 and 50 show how closely the Jurassic species of 
Nautilus approximate, as regards their muscular attachment, to the 
recent Nautilus ; and this analogy may be carried still further back 
in geological time judging by the figure of a Triassic species 
{N. salinarius) given by Mojsisovics in which a considerable por- 
tion of the anterior boundary of the shell-muscle is preserved. 
“ We have lately had the great advantage of examining a specimen 
of the present species from the d’Orbigny Collection of the Museum 
^ Monograph of the Mollusca from the Great Oolite, Pal. Soc. 1850, pt. i. 
p. 10, pi. i. figs. 1, 2. 
“ “ Die Cephalopoden der Mediterranen Trias-Provinz ” (Abh. d. k.-k. geol. 
Peichsanst. Band x.), 1882, pi. xei. fig. 3 a. 
