OKTIIOCERATIDJE. 
103 
Orthoceras, sp. 
This resembles the last one very closely, excepting in its rate of 
increase, which is much more rapid, viz. 1 in 6. It has equally 
numerous septa with 0. cyJindmceum, and may be only a variety of 
that species. 
Horizon. Carboniferous Limestone. 
Locality. Unknown. 
Orthoceras affine^ Portlock. 
? 1836. Orthoceras ovale, Phillips, Geol. of Yorkshire, pt. ii. p. 238. 
1843. Orthoceras affine, Portlock, Pep. on the Geol. of Londonderry 
&c., p. 387, pi. xxvii. f. 9 (not Thoracoceras a-ffine, Fischer). 
? 1845. Orthoceratites ocalis, Murch., Vern., and de Keyserl. Gdol. de la 
Russie d’Europe, vol. ii. p. 3o4, pi. xxv. f. 1. 
18do. Orthoceras ovale, M‘Coy, British Pal. Foss. fasc. iii. p. 572. 
? 1860. Orthoceras ovale, Eichwald, Lethaea Rossica, vol. i. Seconde 
Sect, de I’ancienne Periode, p. 1221, pi. xlix. f. 15, a, h. 
Sp. Char. Shell straight. Section circular, but becoming oval 
towards the aperture. Rate of increase about 1 in 7. Length of 
bodv-chamber nearly twice the basal diameter, with a very per- 
ceptible constriction close to the aperture. Septa direct, distant 
about 5 the diameter of the shell. Siphuucle small, central. 
Surface of the test smooth, or marked with irregular thread-like 
lines. 
Remarks. This species may be identical with Phillips’s 0. ovale, 
but the description given of the latter is much too brief and general 
to be of use, unaccompanied by a figure. It runs thus: — “ Elongate, 
section broad-oval, siphuncle a little eccentric, septa without wave.” 
M‘Coy’s description agrees very well with the species described 
and figured by Portlock under the name of 0. affine, to which I 
refer the specimens in the National Collection. 
This species is distinguished from 0. inequiseptum, Phill., and 
other allied forms, by the greater distance separating the septa. 
Horizon. Carboniferous Limestone. 
Localities. Ireland : Xorthampton ; obtained from a boring 900 
feet deep. The specimen from this last locality was presented by 
H. J. Eunson, Esq., F.G.S. ^ 
Fairly well represented in the Collection. 
Orthoceras pyramidale, Fleming. 
1815. OHhocera pyramidalis, Fleming, Annals of Philo.sophy, vol. v. 
p, 202, pi. xxxi. f. 2. 
1 See an interesting account of borings for water at Northampton in a paper 
by Mr. Eunson in the Quart. Jouru. Geol. Soc. toI. xl. 1884, p. 482. 
