UTUITID^. 7 
length of the entire specimen 1 foot 1 inch and 3 lines ; greatest 
diameter at the aperture 14 inch. 
Re))\arl's. The geographical distribution of Lituites lituus appears 
to be limited to Xorth Germany and Sweden. 
Horizon. Ow7ioee>-as-Limestone ( = Arenig-Llanvirn). 
Locality. Sweden. 
Represented by a single example presented by S. P. Pratt, Esq. 
Litaites ? Ibex, J. de C. Sowerby. 
1839. Lituites ? Ibex, J. de C. Sowerby, in Mm’chison’s Sil. Syst. pt. ii. 
p. 622, pi xi. f. 6. 
18TS. Orthoceras pereleyans, Salter (pars), Mem. Geol. Surv. xol. ii. 
pt. i. p. 354, pi. xiii. f. 4 (not ff. 2, 3, 3 a). 
1849. Hortolus Ibex, d’Orbigny, Prodr. de Paleont. vol. i. p. 27. 
1852. Hotiolus Ibex, M‘Coy, British Pal. Foss. fasc. ii. p. 324. 
1854. Orthoceras pereleya?is, Salter, in Mm-chison's ‘ Siluria,’ pi. xxix. 
ff. 5, 6. 
1873. Orihoceras pereleyans, Salter, Cat. Canibr. and Sil. Foss. p. 187. 
1873. Orthoceras tracheale, Salter, ibid. pp. 187, 192. 
1882. Lituites Ibex, Blake, British Foss. Ceph. pt. i. p. 228, pi. xviii. 
ff . 3, 4, 4 a, 5. 
1839. Orthoceras Ibex, J. de C. Sowerby, in Murchison’s Sil. 
Syst. pi. V. f. 30.] 
Sp. Char. J. do C. Sowerby gives no description of this species, but 
refers to his figure of it as representing “ an arched portion of pro- 
bably Orthoceras Ihex,^^ which therefore approaches to Lituites, but 
we have not seen specimens perfect enough to settle the question. 
Professor Blake (British Foss. Ceph. pt. i. p. 228) states that he 
was unable to find Sowerby 's type specimen, which Salter identified 
with his Orthoceras pereleyans. 
The following is Blake’s description of L. Ibex : — “ The section, 
as Salter states in the description of his 0. pereleyans, is probably 
circular. The flattening always takes place in the plane of cur- 
vature. The radius of curvature is in none so small as in the ty[)e. In 
the smallest, almost reaching the apex, it is -J inch, and the curvature 
gradually decreases as the fragments are of larger diameter — and 
those which show the aperture are nearly straight there ; some also 
may have longer straight portions. The earlier portion forms an 
open coil, tlie whorls not being in contact. The greatest rate of 
increase observed is 1 in 9, and this decreases with the curvature to 
almost zero. The aperture is not contracted, but formed by a 
sigmoid curve, which bends rapidly forward on the convex side as 
to a beak ; it is concave forwards on the side, and curves back to 
