﻿BRITISH FOSSIL CEPHALOPODA. 193 



more than 12°. There is a slight constriction all round. The entire length 

 occupies -f of the greatest diameter. The ventral aperture has a slope of 33 ; it 

 is rather quadrate, with a diameter f- that of the dorsal aperture. The latter is 

 elongate in the antero-posterior direction, and not wider than the ventral; the 

 passage is short and narrow and is the highest part of the shell. The septa have 

 scarcely any convexity, and their distance is ^ the greatest diameter apart. The 

 last chamber, however, is half the ordinary depth, and the 3 before that are only 

 equal to 2. The sutures are direct, and the siphuncle near the centre. The septa 

 appear to have been weak and easily broken down, as they are scarcely indicated 

 in a longitudinal section. The largest has a length of 4 inches, and a maximum 

 diameter of 2-f inches. 



Relations. — A comparison of the characters of this species and of G. ellipticum can 

 leave no doubt that they are very distinct, and that the type of the present is not 

 contorted from the latter. It is far closer to G. obovatum, and difficult to distinguish 

 when the part of the body-chamber containing the aperture is lost or distorted. 



Distribution. — In the Lower Ludlow rocks of Leintwardine (4) and of Aymestry (1). 

 These specimens show clearly the characters, but there are many fragments which 

 might or might not belong to the same species. 



The name has been used pretty indiscriminately for any Gomphoceras, and we 

 thus find it recorded from the neighbourhood of Llandeilo and Woolhope and 

 Malvern, by Prof. Phillips ; from the Lower Ludlow of Dudley, by Grarner ; from 

 the Wenlock Shale of Walsall, and the Wenlock Limestone of Dudley, by Salter ; 

 and in the Lower Ludlow of Coalbrookdale, by the same : but as it is impossible to 

 be in all cases certain of the specimens referred to, it is doubtful if we can conclude 

 more than that a Gomphoceras, something like this, occurs at these places. In the 

 same way, some such species may be recorded from the Upper Ludlow of the 

 Pentlands (2), where a form occurs with a central siphuncle and one side more 

 convex than the other ; also from the Wenlock Limestone or Shale at Dudley, 

 contorted and showing only general shape (4). 



Gomphoceras obovatum, Blake, PI. XXII. figs. 3, 3a. 



Type. — The section at the base of the body-chamber is uniformly elliptical ; the 

 axes being as 32 to 27, and the longer diameter is in the plane of symmetry. On 

 the dorsal side the curvature is nearly uniform from the aperture to the earliest 

 part preserved, with a mean radius of 3 inches ; on the ventral side the septal portion 

 is nearly straight, but the body-chamber rapidly bulges out so as to have a radius of 

 curvature of only 14 lines. The mean rate of increase on the septal portion is 3 in 4. 

 The body-chamber is -f the length of its greatest diameter at the base. The general 

 slope of the aperture is 27°, and the total space occupied is equal to the length of the 

 body-chamber. The ventral opening is elliptic, with diameters of 4" and 10", the 



2 c 



