﻿192 BEITISH FOSSIL CEPHALOPODA. 



of 8 to 5 of the longitudinal. The shells presenting the above characters are usually 

 of considerable size ; namely, with a long diameter of about 3 inches. 



Relations. — The uniformly elliptical shape of the shell with a transversely 

 elliptic section is rare — few such being figured by Barrande ; but it is difficult to see 

 in what respect G. ovum differs from this. There is no difference to which I should 

 attach specific importance if the specimens were found in this country. There 

 cannot be any real confusion between this and G. pyriforme, which was different in 

 both its sections. 



Distribution. — In the Lower Ludlow of Leintwardine (9), of Ledbury (2), and 

 of Herefordshire (1). 



Gomphoceras pyriforme, Sowerby, PI. XXII. figs. 2, 2a. 



1838. Gomphoceras pyriforme, Sowerby in Murchison's ' Silur. System,' pi. 8, fig. 19 (upper). 



1852. „ „ M'Coy, ' Palaeozoic Fossils,' p. 322. 



1873. Phragmoceras pyriforme, Salter, ' Cambrian and Silurian Fossils,' p. 174. 



Type. — This specimen has obviously suffered contortion, and an examination of 

 it alone would readily lead to the belief that it was only an inferior example of 

 G. ellipticum. But other examples show that it is contorted from one less removed 

 from its present shape. Its section is elliptic, the long diameter in the plane of 

 symmetry. The dorsal side has a slight pretty uniform curvature, radius 5-^ inches, 

 up to halfway through the body-chamber. It then makes a rapid curve to the 

 large aperture. The ventral border is sigmoidal, being concave for the first f of that 

 part of the septal portion preserved and becoming convex, with radius 11 lines on 

 the body-chamber. The rate of increase up to the middle of the latter is 1 in less 

 than 2. The aperture is all broken ; but the general direction is nearly horizontal, 

 and the area occupies f- of the greatest breadth of the body-chamber. The septa 

 are distant about -jij- of the diameter at the base of the body-chamber. The sutures 

 are nearly direct. No siphuncle seen. Greatest length, 3§ inches ; greatest diameter, 

 2 1 inches. From the Lower Ludlow, Leintwardine. In the Collection of the 

 Geological Society. 



General Description. — The section in uncompressed specimens on the septal 

 portion is not far from circular — at most the diameters are in the ratio of 8 to 7 — 

 the long diameter being in the plane of symmetry. The curvature gives a 

 convexity on both sides, at least towards the upper part of the septate portion, the 

 dorsal border having a mean radius of 5 inches, and the ventral one of 3j inches. 

 Thus the great bulb of the type is due to compression. The rate of increase has a 

 maximum of 1 in 2. There is a rapid curve on both sides to the aperture, the 

 general direction of which has a very slight slope towards the ventral side, not 



