﻿BRITISH FOSSIL CEPHALOPODA. 219 



ness indicate a direct and simple aperture. If a small specimen, associated in the 

 same rock with some of those here referred to, be rightly considered to belong to the 

 same species, from their rapid increase, from the general character of their ornaments, 

 and especially from the greater strength of ribbing on the front, we learn that the 

 section was more nearly circular in youth, and the curve of the ribs on the front is 

 not so deep. The siphuncle in this is central, and it has not been seen in any other 

 specimen of this species. 



The chief difference between these and the Bohemian type is the rarity of any 

 longitudinal lines, but these are variable, and may easily be lost in the preservation 

 of the fossil. Nevertheless a somewhat similar fossil from the Upper Ludlow shows 

 longitudinal lines, but this may be a distinct species, e.g. Trochoceras Sandbergeri. 

 The septal characters also render the determination doubtful, yet the general pro- 

 portions and ornaments, especially the nature of section, which is rare among Tro- 

 chocerata, the prominence of the ribbing, and the changes in the body-chamber, 

 which are the chief features in the Bohemian, are seen in the English examples. 



Relations. — This species is distinguished from T. giganteurri by the shape of its 

 section and the persistence of the ribs on the front, and from Trochoceras comu- 

 arietis by the proportions of its whorls. 



Distribution. — In the Wenlock Shale, Eastnor Park (3), and in the Wenlock 

 Limestone at Ledbury (2). Also a young form associated with two latter, in the 

 "Woodwardian Museum, labelled a 952, and referred by Salter to Trochoceras gig an- 

 teum. In the Lower Ludlow, Ledbury (2), and possibly in the Upper Ludlow of 

 Presteign, which may be T. Sandbergeri (1). 



Trochoceras speciosum, Barrande, PI. XXIX. figs. 1, 2, and PI. XXVIII. fig. 3. 



1865. Trochoceras speciosum, Barrande, 'Syst. Sil. de Boheme,' vol. ii. pi. 14, figs. 12-15. 



Type. — Barrande's figured specimen shows a rate of increase 1.39, and last 

 whorl .31 of the diameter. The whorls are just in contact and the elevation is very 

 slight. The section is elliptic, with the axes in the ratio of 11 to 9, the longer 

 diameter being in the plane of curvature. The surface has only lines of growth. 

 The body-chamber very slightly leaves the coiled portion. The septa are 28 in 

 half a whorl. They bend rapidly forward to the front, and their surface is very 

 slightly convex in a transverse direction. Siphuncle external and bulbous. Diameter 

 30 lines. The type appears to be unique ; it occurs in stage E, or Upper Silurian, 

 of Bohemia. 



General Description. — Two of the specimens referred to this species show an 

 almost exact correspondence with all its characters, but those that are flattened and 

 distorted do not agree so well. The rate of increase is 1.43, and the last whorl .31 



2 f 2 



