550 MM. Foord and Crick — On Nautilus elegans, Shy. 



from two to four after leaving the umbilicus, so that in the umbilical 

 region they are much wider and coarser than in any other part of 

 the shell. The interspaces dividing the ribs do not exceed one-half 

 the width of the latter. The ribs are on by slightly curved on the 

 sides of the shell, but they form a conspicuous sinus on the peri- 

 phery. The body-chamber is unknown. 



Affinities and Differences. — This species most nearly resembles 

 Nautilus elegans, J. Sow., but differs both in its general form, in the 

 position of the siphuncle, and in the character of its ornaments. 



Horizon and Locality. — Gres Vert (Upper Greensand). Houfleur 

 (Calvados), France. 



Nautilus Atlas, Whiteaves. 



1840. Nautilus elegans, d'Orbigny, Paleontologie Francaise (Terrains Cretaees), 



tome i. p. 87, pi. xix. [Not of J. Sowerby.) 

 1850. Nautilus elegans, d'Orbigny, Prodrome de Paleontologie Stratigraphique, 



tome ii. p. 145. (Not of J. Sowerby.) 

 1853. Nautilus elegans, Sbarpe, Description of tbe Fossil Remains of tbe Mollusca 



found in the Chalk of England (Mon. Pal. Soc), pt. i. Cephalopoda, p. 12, 



pi. iii. fig. 3 ; pi. iv. fig. 1. (iSot of J. Sowerby.) 

 1876. Nautilus Atlas, Whiteaves, Geol. Suit, of Canada, Mesozoic Fossils, vol. i. 



pt. i. p. 17. 



Specific Characters. — Shell inflated, broadly rounded on the peri- 

 phery, which makes a continuous arch with the sides and imparts 

 a semilunate outline to the whorls when seen in section. The 

 greatest bi'eadth of the whorls is therefore a little above the umbilical 

 region. Umbilicus closed. The septa are rather distant, being (type 

 specimen) 1^ inches apart where the height of the whorl, measured 

 from the umbilicus to the median line of the periphery, is 3|- inches. 

 Siphuncle situated considerably above the centre of the septa. Test 

 ornamented with rather strong, prominent, rounded ribs, separated 

 from each other by interspaces equal to about half the diameter of 

 the ribs. The latter make a broad forwardly-directed curve on the 

 sides of the shell, and a broad and shallow sinus on the periphery. 

 Owing to the lateral compression undergone by some specimens, 

 this sinus appears very deep in them, but in uncompressed specimens, 

 of which there are a few in the British Museum collection, the sinus 

 is alwa}'s shallow. The ribs leave their mark upon the cast in the 

 form of faint plications. 



Remarks. — The above description is drawn up mainly from 

 d'Orbigny's figured type ; but there is in the British Museum a 

 fairly good example (No. C. 1027) from the same horizon and 

 locality (Craie chloritee, Bouen) as d'Orbigny's specimen. The same 

 Museum contains also some fairly well preserved English specimens. 



Affinities and Differences. — The inflated form of the present species, 

 the closed umbilicus, and the position of the siphuncle (nearer the 

 peripheral border) are characters which distinguish this species 

 from N. elegans, J. Sow. 



Horizon and Locality. — Lower Chalk. Dover and Burham, Kent ; 

 Lewes and Newhaven, Sussex ; Cliffe Anstey and Calne, Wiltshire ; 

 Ventnor, Isle of Wight; Bouen (Calvados), France. 



