XAUTILID.i:. 
67 
three upon each side of the shell are much stronger and wider apart 
than the rest; there are eight of the ridges upon the ventral (con- 
vex) surface, which are of medium size, Mobile those upon the dorsal 
(concave) surface are much finer. All the ridges are covered with 
discontinuous transverse lines or lamellm, which form conspicuous 
nodes where they cross the former. 
Remarhs. This species is readily distinguished by its open whorls 
and by the character of its ornaments. 
It is stated by de Kouinck to have been found in the black lime- 
stone of Parkmore, in the county of Limerick, a specimen from that 
locality having been sent to him by Mr. AY. H. Baily of the Geolo- 
gical Survey of Ireland. 
Horizon. Calcaire Carbonifere (Assise TI.)= Carboniferous Lime- 
stone. 
LocaliUj. A^ise, Belgium. 
Kepresented in the Collection by a small fragment. 
Gyroceras serratum, de Koninck. 
1844. Gip'oceras serratum, de Koninck, DesCr. des Auim. Fossiles du 
Terr. Carb. de la Belgique, p. 533, pi. xlviii. ff. 2, a, b. 
1849. Xautiloceras serratum, d'Orbignv, Prodr. de Paldont. Stratigr. 
vol. i. p. 112. 
1880. Gyroceras serratum, de Koninck, Faune dii Calc. Carb. de la 
Belgique, pt. ii. (Annales du AIus. Boy. dTlist. Nat. de Belgique, 
tom. v.) p. 10, pi. xxxii. fF. 5, oa, bb. 
Sp. Char. Shell composed of one and a half or two whorls, com- 
pletely out of contact, and with an obtuse initial point. The trans- 
verse section (except quite at the apex) is scutiform, the ventral or 
convex side forming a flattened area, which is bounded on either 
side by prominent raised areas, the whole increasing in breadth 
with the growth of the shell. The sides slope somewhat abruptly 
inwards to the concave border. The septa appear to be numerous, 
strongly concave, and the sutures bent backwards at the sides of the 
shell. The body-chamber occupies nearly ^ of the last whorl. 
The siphuncle is situated a little above the centre. The ornaments 
of the shell consist of twenty-two prominent, longitudinal, jjarallel 
ridges, studded with small tubercles. On the convex side of the 
shell there are ten ridges, three of which on either side form two 
raised bands, marking off the central flattened area. Upon the 
latter are the four remaining ridges, the two centre ones being 
much stronger than those on each side of them. The remaining 
twelve ridges, which are all of equal strength, occupy the sides and 
inner border of the shell. The ornamentation here shows no trace 
of the contact of a previous whorl. 
F 2 
