﻿BRITISH FOSSIL CEPHALOPODA. 155 



specimen described by M'Coy follows Sowerby's. As to 0. marloense of Phillips, 

 I can find no justification for its establishment. The curvature shown is due solely 

 to the dislocation of the upper part, the lower two-thirds having absolutely straight 

 sides. Phillips says it differs also from 0. imbricatum in having closer and more 

 oblique septa. A comparison of the figures, however, and of Phillips's type, shows 

 that the latter has, if anything, more remote and less oblique septa. There is very 

 little difference between this and 0. Morrisi of Barrande. 



Distribution. — The shell occurs in the Wenlock Shale of Middleton (1), Marloes 

 Bay (Phillips's specimen), Dudley (4), and Coldwell (1) ; in the Wenlock Limestone 

 of Dudley (1) ; in the Lower Ludlow, Ledbury (1) ; in the Upper Ludlow of 

 Ludlow (1) and Treverne Hills (1) ; in the Tilestones of Storm Hill (1) ; also in 

 Upper Silurian Beds of Ferriter's Cove (1). Septal surfaces are found only in the 

 Upper Ludlow, or in rocks of undefined Upper Silurian age. They are abundant at 

 Ludlow (16), and in the Pentland Hills (11), and occur also at Mortimer's Cross (1), 

 Wenlock (2), Stoke Edith (1), Bishop's Castle (2), Presteign (3), Aymestry (1), 

 Treverne Hills (2), and Usk (2). As, however, it has been seen that a ribbed species, 

 0. kendalense, also found in the Upper Ludlow, shows similar veined septal surfaces, 

 some of the examples referred to the present species may belong to the latter. 



Fossils by this name are also recorded by Phillips from Llandeilo, Woolhope, 

 and Abberley ; by Griffiths, from Egool, and in the Catalogue of Western Scottish 

 Fossils, from Ardmillan Braes ; and under the name of 0. marloense, by Salter, from 

 the Upper Ludlow, Coalbrookdale. 



Orthoceeas perversum, Blake, PI. XVI. figs. 1, 2. 



Syn. ? 1839. Oethoceras imbricatum, Sowerby in Murchison's 'Sil. Syst.' pi. 9, fig. 2, p. 620. 

 1852. „ „ M'Coy, 'Pal. Foss.' p. 315. 



1873. „ „ Salter, « Camb. and Sil. Fossils,' p. 187. 



Type. — Section elliptic, the diameters in the ratio of 7 to 6 ; rate of increase of 

 the long diameter 1 in 21 in the septate portion, reducing to 1 in 36 in the body- 

 chamber. This is 3^ inches long, which is more than 1\ times its basal diameter ; 

 about 1 inch from the base is a broad and shallow thickening of the shell, f inch in 

 breadth. The aperture is simple. The shell exfoliates in two layers, the outer one 

 being thinner and lighter in colour, and having feeble undulations of growth in the 

 body-chamber. The septa are irregularly undulating, and distant \ the diameter. 

 Their convexity is equal to two chambers or f- the diameter. The siphuncle is of 

 moderate size and unsymmetrically situated, -^ along the greater diameter and \ 

 along the smaller. The septa are lowest opposite the siphuncle. The greatest 

 diameter is 1^ inches, and the length is 9 inches. From the Upper Ludlow, 

 Ludlow. In the Museum of Owens College, Manchester. 



x 2 



