260 
NAUTILOIDEA. 
all the specimens that I have had the opportunity of examining 
wanting a considerable portion of the apex. The septa are nu- 
merous, being about 3 lines distant from each other where the shell 
has a diameter of 2 inches ; the last two septa are much nearer 
together than the preceding ones. The septa have a slightly sigmoid 
obliquity corresponding to the dorso-ventral diameter of the shell. 
The siphuncle is much inflated between the septa, giving it a moni- 
liform appearance when seen in a longitudinal section. It is mar- 
ginal in the young shell, but recedes a little towards the centre in the 
adult. The test is moderately thick, with a perfectly smooth surface, 
or with very obscure transverse lines, to be seen only in well pre- 
served specimens. One of the specimens has a series of faint longi- 
tudinal ridges in the constriction just below the aperture. There is 
a slightly raised rim at the base of the body-chamber, seen only 
upon casts of that portion of the shell. 
BemarTcs. This fine shell is distinguished from Poterioceras ven- 
t7'icosum, its nearest ally, by its much more slender proportions. 
One of the specimens figured by Sowcrby (loc. cit. fig. 2) under 
the name “ Orthocera fusiformis ” represents a Cyrtoceras^ and it will 
therefore be found described under that genus. 
Horizon. Carboniferous Limestone. 
Localities. Bolland, Yorkshire ; Kildare, Kaas, Cork, Ireland. 
Kepresented in the Museum Collection by a very fine series of 
examples, including the one from Bolland figured by Phillips {loc. 
cit.), which is now contained in the “ Gilbertson Collection.” 
Poterioceras cordiforme, Sowerby, sp. 
1821. Orthocera cordifo7'mis, Sowerby, Min. Conch, vol. iii. p. 85, 
tab. ccxlvii. 
1828. Orthocera cordifoinnis, Fleming, Hist, of British Animals, p. 238. 
1844. Poterioceras ventricosum, M^Coy, Synop. Carb. Foss, of Ireland, 
p. 10, pi. i. f. 2. 
1849. Gomphoceras cordifoi'me, d’Orbign}q Prodr. de Paleont. Stratigr. 
vol. i. p. 112. 
1849. Gomphoceras ventricosum, d’Orbigny, ibid. 
1852. Gomphoceras cordiformis, Giebel, Fauna der Vorwelt, Band iii. 
Abth. i. p. 216. 
1876. Poteriocei'as cordiforme, Armstrong, Young, and Bobertson, Cat. 
of Western Scottish Fossils, p. 59. 
1876. Poterioceras ventricosnm, Armstrong, Y^oung, and Bobertson, ibid. 
Sp. Char. Shell very large, fusiform, much inflated, so that the 
width amounts to nearly half the length. Circular in cross section. 
The proportions of the body-chamber relative to the entire shell 
