﻿222 BRITISH FOSSIL CEPHALOPODA. 



sequently is less, and the section becomes more rounded on the front. There is no 

 certain contraction at the aperture. The septa are equally close ; the siphuncle is 

 in the same position, and has a slightly bulbous form. 



Relations. — -This seems to agree in every respect with Barrande's Trochoceras 

 oxynotum, and the section and other characters are so remarkable, even as shown by 

 Sowerby, that it is rather astonishing that Barrande should have made no reference 

 to it, but have passed it by as a Cyrtoceras. 



Distribution. — In the grey mudstone, ? Lower Ludlow, of Dudley (1), and in 

 limestone referred to in the Lower Ludlow near Welchpool (1). 



Trochoceras striatum, Blake, PI. XXIX. fig. 5 ; and PI. XXX. figs. 3, 4, 4a, 46. 



Type. — The rate of increase is 1.74, and the last whorl is .4 of the diameter. 

 The want of symmetry is very slight. The section is uniformly rounded, but 

 rather flattened. The body-chamber continues the same curve as the earlier 

 portion. The ornaments are 33 almost obsolete, rounded, subseparate ribs, curving 

 very rapidly backwards, and these die away on the body-chamber, leaving only 

 lines of growth. The septa are 24 per whorl, and the sutures are somewhat sigmoid, 

 commencing by being slightly convex towards the aperture, on the inner edge. 

 There are some bulbous-looking bodies on the circumference, which may represent 

 an external beaded siphuncle. Diameter 3 inches. From the Lower Ludlow, 

 Ledbury. In the collection of Dr. Grindrod. 



General Description. — Other examples confirm the great rapidity of growth, 

 and the breadth of the outer whorl. The thickness is about ^ the breadth, and in 

 some there are very good indications of asymmetry. The body-chamber is not 

 longer than its basal diameter, and the aperture is formed of a gentle sigmoid back- 

 ward tending curve parallel to the lines of growth, about -|- the diameter apart 

 (PI. XXX. fig. 3). The shell, when well preserved, is covered by fine lines parallel 

 to the ribs, which are most conspicuous towards the convex border (fig. 4a), while 

 epidermids cover the region near the concave border (fig. 46). The septa are 

 pretty uniformly concave ; except near the inner border, their transverse convexity 

 is slight; and their number pretty constant at 24 per whorl. The siphuncle is not 

 certainly determined. 



Relations. — Flattened examples of Nautilus quadrans may be taken for this 

 species until one is familiar with its aspect, when it is unmistakable from its delicate 

 ornaments and graceful contours. Cyrtoceras compressum is also somewhat similar, 

 but the septa in that species are much closer, and of course the curvature is not 

 so great. 



Distribution. — In the Wenlock Shale, Usk (5) ; in the Lower Ludlow, 

 Ledbury (2). 



