﻿204 BRITISH FOSSIL CEPHALOPODA. 



1^ inches; the length is 2§ inches. From the Wenlock Limestone, Dudley. In the 

 Woodwardian Museum. 



General Description and Relations. — This is a specimen which I cannot satisfac- 

 torily fix to any known species. It has the aperture of 0. imbricatum, but not its 

 shape of section or rate of increase ; but the obliquity of the aperture is the distin- 

 guishing feature. No signs of ornament tempt us to place it with P. ventricosum. 



Distribution. — In the Wenlock Limestone of Dudley (1), and possibly in the 

 Lower Ludlow of Ledbury (1). 



Phragmoceras subexternum, Blake, PI. XXV. fig. 3. 



Type. — Section elliptic, with the shorter axis in the plane of curvature, the ratio 

 being 8 to 9. Curvature only perceptible on the convex side, the other side being 

 nearly straight. The rate of increase is 2 in 5 on the septal portion. The body- 

 chamber continues to increase till near the aperture, when the convex side turns 

 round rapidly, so as to be within 45° of the horizontal ; but the aperture is not seen. 

 The ornaments consist of irregular rugosities sloping back to the convex side, covered 

 by parallel lines of growth ; the former about 20 per diameter. The septa have 

 only a slight convexity ; they may be very close, but their position is not certainly 

 seen. The suture of the last slopes backwards towards the convex side parallel to 

 the ornaments. The siphuncle is small, and situated f of the diameter from the 

 convex side. Greatest length, 3£ inches ; greatest diameter, 1\ inches. From the 

 Wenlock Limestone of Ledbury. In the collection of Dr. Grindrod. 



General Description. — The type is unique. 



Relations. — The extraordinary position of the siphuncle, either for a Phragmoceras 

 or a Gomphoceras, renders few comparisons possible. The ornaments place it rather 

 near to G. imperiale, but that has no curvature. One might also think of Orthoceras 

 Barrandei, but that species seems to come to a termination without any ingrowth 

 towards the aperture. 



Distribution. — In the Wenlock Limestone of Ledbury (1). 



Phragmoceras arcuattjm, Sowerby, PI. XXVI. figs. 1, 2, la, and 



PL XXV. fig. 1. 



1838. Phragmoceras arcuatum, Sowerby in Murchison's • Silurian System,' pi. 10, fig. 1a, p. 621, not 

 var. a (includes P. ventricosum, fig. 5, but not figs. 4, 6). 



Type. — This I have not been able to discover, but the figure given by Sowerby 

 is fairly characteristic. Section unknown, apparently elliptic, with the longer axis 

 in the plane of curvature, and axis not very unequal. The mean radius of external 

 curvature is If inches, with a mean diameter of 1^ inches. The rate of increase 



