NAniLID^. 
125 
1878. Xauriliis sulcifer, de Koninck, Faiine dii Calcaire Carbonifere de 
la Belgique (Annales du Mas. Roy. d’Hist. Nat. de Belgique, 
tom. ii.), p. 130, pi. xxvii. ff. 12 a, 12 h. 
Sp. Char. Shell thick, discoid, composed of three shghtly em- 
bracing whorls, all exposed in a deep umbilicus, which has a small 
central perforation. The transverse section is siibcordiform and 
one third wider than high. The sides are very narrow and inflated, 
with a keel bordering the edge of the umbilicus in the young shell, 
which becomes obsolete in the adult. The periphery is occupied by 
a verj’ prominent raised band, channelled in the centre, on each 
side of which there is an abrupt slope towards the edge of the um- 
bilicus, and upon these slopes the young shell bears three keels or 
ridges, which gradually disappear as the shell advances in growth. 
The body-chamber occupies about half of the last whorl. 
The septa are moderately distant from each other ; about twenty- 
three may be counted in a single volution of a young example 
whose greatest diameter is 15 lines. The sutures are slightly 
sinuous upon the sides, and form a slight, backwardly directed siuus 
upon the periphery. 
The siphuncle is slender, and is situated a little above the centre. 
The test is unknown, aU the specimens collected being casts. 
The surface of the cast is, however, beautifully marked with a series 
of fine, transverse, sinuous incised lines, which in some parts of the 
body-chamber become broken up into dotted lines. These markings 
are seen upon the cast of the septate part of the shell as well as on 
that of the body- chamber, and they are evidently similar to those 
described in Ccelonautilus cariniferus and C. paucicar hiatus^ and 
must have had the same origin h 
Remarlcs. The following observations concerning the American 
examples of this species are taken from Messrs. Meek and Hayden’s 
description (Joe. cit. p. 163). “ This species bears some resemblance 
, to certain varieties of X. siilcatus of Sowerby, as figured by de Kon- 
inck (Anim. Foss. pi. xlvii. fig. 10, and pi. xlviii. figs. 8, 9), but 
differs in the number and arrangement of its revolving angles, and 
in the possession of longitudinal striae. It is still more nearly allied 
to X. Edwardsianus, de Koninck (Suppl. Anim. Foss. pi. lix. figs. 
I 7, «, h, c), but differs in having less compressed whorls which are 
rounded instead of angular around the umbilicus, while its dorsal 
i ^ Similar markings have been noticed and figured by Barrande, who ascribes 
them to the same cause (see Syst. Sil. de la Boheme, 1868, vol. ii. pi. cclxxxiii. 
{Orthoceras suhannidare, Miinst.), pi. cccii. (0. severurn, Barr.), and numerous 
species besides). They may also be conqjared with the impressions of the 
' surface of the mantle so admirably preserved in many specimens of Geoteuthis 
^ from the Lias and Oxford Clay, and of Flesioteuthis from the Solenliofen Slates. 
I 
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