﻿198 BRITISH FOSSIL CEPHALOPODA. 



convexity on both sides, with radius of curvature 2i inches; thus forming rather a 

 butt-shaped shell, both ends being more or less truncate. The body-chamber does not 

 commence till the contraction has set it ; its length is -f of its basal long diameter. 

 The aperture is produced, the shell having been thickened all round it. Its general 

 direction is nearly horizontal, and it occupies nearly the whole of the upper surface. 

 The ventral opening is round ; the dorsal opening appears to consist of two nearly 

 closed lobes of nearly the same size as the ventral opening, united to the passage 

 and thereby to one another, by narrower branches. The dorsal border is thus 

 concave, and is ■§■ as long as the ventro-dorsal axis of the aperture. The passage is 

 rather long and narrow. The septa have a very slight convexity, and are more 

 conical than spherical. They are distant -^ T the greatest diameter. The sutures 

 are direct, and the siphuncle is central. Greatest length, 41 lines ; greatest 

 diameter, 25 lines. From the Lower Ludlow near Aymestry. In the Woodwardian 

 Museum. 



General Description. — Only one other specimen has been seen from the same 

 locality, and this adds nothing to the type beyond confirming its principal 

 characters. 



Relations. — Even without the aperture the generally elliptic shape of the whole, 

 combined with its central siphuncle, separates this species from G. pyriforme on the 

 one hand, and G. ellipticum on the other. G. eta has an aperture of the same type, 

 though with minor differences ; but the shape of the shell is not the same. From 

 G. aquale it is distinguished by its aperture. G. Haueri of Barrande is very close 

 to this, but the dorsal lobes of the aperture are not expanded, and the septa have a 

 considerable convexity, while the siphuncle is scarcely central. 



Distribution. — In the Lower Ludlow rocks of Aymestry (2). 



Gomphoceras amygdala, Barrande, PI. XXV. figs. 4, 4a, 45 ; 

 PI. XXIII. figs. 1, 7a. 



1865. Gomphoceras amygdala, Barrande, ' Syst. Silur. de Boheme,' pi. 77, figs. 23-26 ; and 



pi. 80, figs. 1-17, p. 273. 



Type. — The section varies from nearly circular, especially at the smaller end, to 

 a transverse ellipse, with axes in the ratio of 5 to 6. The ventral side has more 

 convexity than the dorsal. The rate of increase on the septal portion is at the rate 

 of 1 in a little less than 3. The body-chamber does not decrease much ; its length 

 is about | the basal diameter. The aperture has no very marked constriction round 

 it ; it occupies about § the greatest diameter. The dorsal opening is a transverse 

 rather quadrate ellipse, whose boundaries rather vary. The ventral opening and 

 the passage are scarcely distinct, and have about the same width as the dorsal 

 opening ; the apex lies between the two. The septa have a convexity of ^ their 



