﻿224 BRITISH FOSSIL CEPHALOPODA. 



the parallel lines of growth on the ribs, but often the epidermids of the under-layers 

 are visible. These are direct, crossing the ribs, from 14 to 22 per line. There 

 are also longitudinal ones on the inner side when exposed. The body-chamber 

 always includes part of the normally-coiled portion, and extends a variable distance 

 in a nearly straight line. The largest seen was 8 inches long, but it is impossible 

 to say what proportion this bore to the coiled portion. This and several smaller 

 ones show no difference on approaching the aperture, which seems to be indicated 

 by the deeply back-curving ribs ; but in one or two instances there is a decided 

 contraction just at the aperture on each side of the whorl, as in fig. 2, dividing it, as 

 seen in full view, into two wider portions, separated by a narrower, and yet not 

 forming a contracted aperture in the same sense as in the Phragmocerata. The 

 septa are direct across the front ; but on the sides, their general direction being 

 radial, they become concave at some part, so that they cut across the ribs, and do 

 not coincide with the epidermids, and they thus on the whole become sigmoid in 

 form. They do not bear a fixed proportion to the ribs, but are sometimes more, 

 sometimes fewer, the last few being closer, up to -j^- the whorl-breadth. The con- 

 vexity of the septal surface is pretty constant at about £ the whorl-breadth. The 

 siphuncle is nearly invariable, a little beyond the centre. 



Relations. — The chief difficulty about this species is the decision of its genus. It 

 has undoubtedly a considerable portion uncoiled, and might therefore be a Lituites. 

 On the other hand, it is unsymmetrical, as seen in fig. 2, which has a complex 

 aperture, and hence should be a Trochoceras. I prefer the latter interpretation, 

 as the straight portion forms a comparatively small part of the shell compared with 

 that of the true Lituites, and it has not been satisfactorily proved that the whorls of 

 the latter genus are ever in contact. 



Distribution. — In the Wenlock Shale of Dudley (3) ; in the Wenlock Limestone at 

 Wenlock (1) and Dudley (3) ; abundant in the Lower Ludlow of Leintwardine (10), 

 also of Ledbury (18), in the collection of Dr. Grindrod ; in the same horizon at 

 Usk (1) and Llanbadock (1), and in the neighbourhood of Cardiff (1). 



M'Coy in his ' Palgeozoic Fossils ' records this species from Upper Bala, Builth ; 

 but I have seen no true representative of it in those beds. It is also recorded by 

 Professor Phillips, from Upper Silurian at Llandeilo and Abberley ; by Professor 

 Hughes, from the Coniston Flags ; and by Salter, from the Coniston Grit, and from 

 the Lower Ludlow, at Parkes Hall, Staffordshire, and at Coalbrookdale. 



