52 
NAUTILOIDEA. 
Herefordsliire ; Llangollen, Denbighshire; Usk, Panteagne, Mon- 
mouthshire; Llandegfydrl, North (?) Wales. Specimens from the 
two last-named localities were presented by J. E. Lee, Esq., F.S.A., 
E.G.S. 
Eepresented in the Collection by numerous examples. 
Orthoceras Gra3ri, Blake. 
1882. Orthoceras Gray*, Blake, Brit. Foss. Ceph. pt. i. p. 102, pi. xiii. f. 6. 
>Sp. Char. Section elliptical, the diameters in the ratio of 5 to 4. 
Bate of increase of the long diameter 1 in 5 in the type specimen. 
The septa are 2° or 3° oblique, and about i the long diameter apart. 
The siphuncle appears to be central. The ornaments consist of 
subacute, subseparate ribs | the long diameter apart. The body- 
chamber is unknown. 
BemarTcs. This species is distinguished from 0. ibex by its rate 
of increase and larger size, and from 0. anmdatum by the same 
characters and also by the absence of fimbriation in the transverse 
riblets. 
Horizon. Wenlock Limestone (Salopian). 
Locality. Dudley, Worcestershire. 
Eepresented by the type, described by Prof. Blake. 
Orthoceras dimidiatum, Sowerby. 
1839. Orthoceras dimidiatmn, Sowerby, in Murchison’s Sil. Syst. p. G20, 
pi. viii. f. 18. 
1849. Orthoceras suhdwudiatmn, D’Orbigny, Prodr. de Pal. vol. i. p. 28. 
1852. Orthoceras dimidiatum, M‘Ooy, British Pal. Foss. fasc. ii. p. 314. 
1852. Orthoceras dimidiatum, Salter, id. Appendix A, p. vii. 
1873, Orthoceras dimidiatmn, Salter, Cat. Cambr. and Sil. Foss. p. 98. 
1882. Orthoceras dimidiatum, Blake, Brit. Foss. Ceph. pt. i. p. 103, 
pi. vi. ff. 11, 12. 
[Ah^ 1840. Orthoceratites dimidiatus, Minister, Beitr. zur Petrefracten- 
kunde. Heft iii. Taf. xix. ff, 2, 5.] 
B-p. Char. Section not seen. Average rate of increase 1 in 16. 
The septa vary in their distance from -1 to more than | the diameter. 
The body-chamber is several times the length of its basal diameter. 
The siphuncle is unknown. “ The ornaments are semi-ribs, found 
only on the right side of the specimen ; these are slightly undu- 
lating, but rather oblique, rising to the left side ; and are the 
mean diameter apart, and consist of downward imbrications which 
gradually die away” {Blake). The imbrication may be either 
upward or downward. 
