XATJTTLID.i:. 
133 
angular. The inner whorls are covered to the extent of at least 
two thirds hy those which succeed them. The section is trans- 
versely reniform ; the siphuncle is situated a little above the 
centre. The surface of the test is quite smooth, nothing but faint 
lines of growth being observable upon it. 
Horizon. Calcaire Carbonifere supcrieur de Vise (Assise vi.) = 
Carboniferous Limestone. 
Localities. British. Isle of Man. — Foreign. Vise, Belgium. 
Eepresented in the Collection by three examples. 
Coelonautilus infundibulum, de Koninck, sp. 
1878. Nautilus infundihulum^ de Koninck, Faiine dii Calcaire Carho- 
nifere de la Belgique (Annales du Miis. Roy. d’flist. Nat. de 
Belgique, tom. ii.), p. 104, pi. xxiv. ff . 1 a, 1 b. 
Sp. Char. SheH thick, discoid, composed of three or four whorls, 
all exposed in a moderately deep umbilicus. Each whorl covers 
about half of the preceding one. The whorls in the young shell 
are keeled in the middle of the sides, the amount of involution of 
the whorls being exactly limited by the keel, so that the latter is 
not seen in an adult shell, being hidden by the succeeding whorls. 
The keel, however, disappears entirely as the shell increases in 
growth, that is after the first whorl, and the sides of the umbilicus 
become rounded, though still abruptly sloping. The centre of the 
periphery in the young shell is occupied hy a prominent fiattened 
elevation, with angular borders, and there is an appearance in a 
very young specimen of there having been two or more keels on 
each side of the elevation, but the surface of the specimen does not 
show this distinctly. On each side of the elevation there is a 
gradual slope down to the keel, already described as forming the 
border of the umbilicus. The periphery and also the sides become 
flattened after the completion of about one and a half whorls, and 
the section of the shell now assumes a subquadrate form, but with 
rounded angles. 
The septa are not very numerous : there are nineteen or twenty 
in a complete whorl in the specimen figured. The siphuncle is 
situated a little above the centre. The test is almost smooth, only 
lines of growth being visible upon it with the aid of a lens. 
Remarks. A single imperfect example only of this species is 
stated by de Koninck to have been found in the ‘ Calcaire Carbo- 
nifere superieur’ of Vise (Assise vi.), but having seen a fine 
, specimen in Mr. James Thomson’s Collection, from the black lime- 
: stone of Castlecary, near Glasgow, he used it to supply what was 
i wanting in the Belgian specimen. 
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