﻿BRITISH FOSSIL CEPHALOPODA. 209 



the length of the shell. Greatest length, 4f inches; greatest diameter, nearly 

 2 inches. From stage E or Upper Silurian of Bohemia. 



General Description. — Only one British specimen showing similar characters has 

 been seen, and that is but a fragment. Its section is a uniform ellipse, with the axes 

 nearly in the ratio of 2 to 1, although from the hardness of the matrix it does not 

 appear to have been compressed. The ornaments are fine transverse riblets, about 

 7 per line. The septa have a convexity of -^ their diameter, and slope back to the 

 convex side (the specimen being only half preserved, the other side alone is seen) ; 

 siphuncle ^ the diameter from the convex side ; sigmoid septa at least four in 

 number : they make very sigmoid curves so as to cut the opposite side at an obtuse 

 angle, and they succeed each other vertically. One of the surfaces seen at the end 

 (fig. 10a) is convex from back to front, and concave from side to side. 



Relations. — It may well be doubted if our British specimen is indeed A. bohemi- 

 cum, — its section is different, and the septal convexity is greater ; but as these 

 differences may arise from compression, there are no ample grounds for their 

 separation. 



Distribution. — In the Upper Ludlow of Whitecliffe, Ludlow (1). 



Ascoceras vermiforme, Blake, PI. XXVI. fig. 8. 



Type. — The section is not seen, the curvature is very slight, the radius being 

 about 4 times the greatest breadth. The length is about the same multiple of it ; 

 the aperture is more than f- of the same. The ornaments are slightly undulating, 

 nearly direct, upward imbrications, about 6 per line. The septal characters are not 

 well seen, and no siphuncle is visible ; the sigmoid septa are also obscure, — there do 

 not appear to be more than two, and these, if really present, are only slightly sigmoid. 

 Greatest length, 14 lines; greatest breadth, 4 lines. From the Lower Ludlow of 

 Ledbury. In the collection of Dr. Grindrod. 



General Description. — Another specimen of this species, which is the one to 

 which the above-adopted name was applied, in the Museum of Practical Geology, 

 by Salter, shows the same proportionate dimensions, curvature, and ornaments, 

 and indicates that the second sigmoid septum was nearly parallel to the convex 

 border, meeting the opposite side at an acute angle. This specimen is nearly 

 2 inches long. 



Relations. — By the formation of its sigmoid septa, this is more nearly allied to 

 A. Barrandei than to A. bohemicum, but differs from both in being so much narrower 

 in proportion. The Bohemian forms that have the same shape appear to be either 

 smooth or strongly ribbed- 



Distribution. — In the Lower Ludlow of Ledbury (1) and in the Upper Ludlow of 

 Ludlow (1). 



2 E 



