50 
NAUTILOIDEA. 
shell the annulations disappear rapidly and completely. The larger 
ornaments are covered with transverse parallel riblets, and these 
also tend gradually to become obsolete towards the aperture. 
Horizon. Wenlock Limestone. 
Locality. Dudley, Worcestershire. 
Well represented in the Collection. 
Orthoceras Maclareni, Salter. 
1839. Orthoceratite, Maclaren, ‘ A Sketch of the Geology of Fife and 
the Lothians/ p. 203. 
1854. Orthoceras Maclareni, Salter, in Murchison’s ^ Siluria,’ Foss. 
Group 25. 
1861. Orthoceras Maclareni, Salter, Mem. Geol. Surv. of Scotland 
Sheet 32, p. 143. 
1865. Orthoceras Maclareni, Haswell, ^ On the Silurian Formation of 
the Pentland Hills,’ p. 23, pi. i. f. 2. 
1873. Orthoceras Maclareni, Salter, Cat. Cambr. and Sil. Foss. p. 186. 
1882. Orthoceras Maclareni, Blake, British Foss. Ceph. pt. i. p. 105 
pi. vi. ff. 7-10. 
Sp. Char. Shell straight. Section elliptical ; but the specimens 
are all compressed. Septa direct, with a convexity of 4 the long 
diameter ; they are distant | the diameter. Siphuncle central ; sui’- 
face ornamented with “ strong, sharp ridges, imbricating upwards ; ” 
their distance is variable, from ^ to ^ the diameter, or even less ; 
they have an irregular imbrication. 
Remarks. The species most nearly allied to this is 0. Duponti ; 
but that has ornaments which, though irregular, may be described 
as true ribs, whereas in the present species they are rather irregular 
transverse folds. 
Horizon. Ludlow (exact division unknown). 
Locality. Usk, Monmouthshire. 
Fairly well represented in the Collection by specimens presented 
by J. E. Lee, Esq., F.S.A., F.G.S. 
Orthoceras tracheale, Sowerby. 
1839. Orthoceras traeheale, Sowerby, in Murchison’s Sil. Syst p 604 
pi. hi. f. 9 5. • E* . 
1852. Orthoceras traeheale, M‘Coy, British Pal. Foss. fasc. ii. p. 321. 
1854. Orthoceras traeheale, Salter, in Murchison’s ‘ Siluria ’ pi xxxiv 
f.6. . e- • 
1882. Orthoceras traeheale, Blake, Brit. Foss. Ceph. pt. i. p. 97, pi. v.f. 6. 
[P1848. Orthoceras perelegans,'&dlter, Mem. Geol. Surv. vol ii.pt i 
pi. xih. fE. 2, 3 (not f. 4)v] 
Sp. Char. The section in weU-preserved examples is circular. 
