264 G.C. Crick—Gigantic Cephalopod Mandible. 
surface), 33°2mm. Viewed laterally the median line of the hood is 
feebly convex; that of the shaft feebly concave, especially the portion 
near the hood. The ‘ profile-curvature’ angle, or the angle which 
the median line of the ‘hood’ makes with the median line of the 
‘shaft’, is 94°. The hood has a prominent obtuse median ridge, the 
sides of the hood forming an angle of 109° with each other. Near 
the anterior and inner border there is a series of longitudinally- 
elongated pits, closed anteriorly but open posteriorly, that may 
perhaps have been caused by a fringed lip such as was described by 
Sir Richard Owen in the recent Vautilus pompilius,! and on the 
posterior portion of the hood there are some coarse obscure longi- 
tudinal ridges. The outer surface of the shaft bears both longitudinal 
and transverse feeble rounded ridges, giving the surface an obscurely 
reticulated appearance. On each side of the shaft close to the hood 
there are remains of the chitinous portion (marked / in figs. 2a and 6) 
of the mandible. Viewed laterally the inner surface of the mandible | 
is feebly sigmoidal, the anterior portion being concave and the 
posterior part convex. The anterior two-thirds of this surface is 
occupied by a protuberance which is widest at its posterior part, being 
there about 10 or 11mm. wide, and anteriorly narrows and also 
becomes much less prominent. The hindermost part of the inner 
surface has several deep irregular depressions. The angle of the 
hood as seen from the inner side is 61°. 
As to the affinities of the fossil, it most nearly resembles the 
specimen which d’Orbigny? described and figured in 1825 from 
the Corallian rocks of the Chez promontory, near La Rochelle, 
France, under the name of Rhyncholithes giganteus, and which was 
found in the same bed as a large Nautilus, which he named JVautvlus 
giganteus, that attained a diameter of 18 or 19 inches and was the 
only Cephalopod found in the bed which yielded the mandible. 
According to d’Orbigny’s figures that specimen was longer and 
narrower than the present eamiplel: its extreme length and breadth 
being 54°8 mm. and 31°2mm. respectively, the angle at its apex, as 
seen from the inner side, being 48°; also the swelling on its inner 
surface extends farther backward than in the present example. 
We are then led to ask if any Inferior Oolite Nautilus is known 
sufficiently large to have owned such a mandible. Dr. Foord and the 
present writer ‘described ® in 1890, under the name Wautilus ornatus, 
a species of WVautilus from the Inferior Oolite that attained 
a considerable size, for the British Museum collection contains 
an example‘ [ No. C. 578] of the species 16 inches in diameter from 
a quarry near Oborne Church, near Sherborne, Dorset, and another 
2 feet in diameter from the Inferior Oolite of Sherborne [_No. C. 3193}. 
he mandible above described might then have belonged to a large 
example of such a species. 
1 R. Owen, op. cit., p. 22. A Soa similar series of pits is figured by 
Foord (Cat. Foss. Ceph. Brit. Mus., pt. 2, 1891, figs. 78d, e, f) in an upper 
mandible from the Lias of Lyme Regis, that Dr. Till has subsequently (Jahrb. 
d. k.k. geol. Reichsanst., Wien, Bd. lvii (1907), Hft. 3, p. 539) named 
Nautilus (Rhyncholithes punctatus) nom. nov. 
2 A. d’Orbigny, Ann. Sci. nat., ca v, 1825, pp. 215-17, pl. vi, Be) Li 
3 Ann. Mag. Nat. Hist., [6], vol. v, p- 273, fig. 7. 
* Presented by George Potter, Esq., . R.M.S. 
ae 
