﻿92 BRITISH FOSSIL CEPHALOPODA. 



species, and most probably to our present one, of which it would be a valuable 

 example, the nearest approach to it being the specimen represented by fig. 7. 



Distribution. — The examples of this species from the Bala Series of Sholeshook (4), 

 as seen in the Museum of Practical Geology, and of Owens College, Manchester, 

 are perfectly characterised, and leave no doubt of its existence during the Lower 

 Silurian period. The example recorded by Salter (' Camb. and Sil. Foss.' p. 90), from 

 the May Hill Sandstone, may belong to 0. ibex. Throughout the Upper Silurian it 

 is abundant, though more characteristic of the Lower beds. It occurs first in the 

 Upper Llandovery of the Onny river (1) ; then in the Woolhope Limestone of Old 

 Radnor (4), Littlehope (1), and Usk (1) ; in the Wenlock Shale of Barr (1), Cheney 

 Longville (2), Malvern (1), Onny river (1), Usk (1), and Dennydd fawr(l); in 

 the Wenlock Limestone of Dudley (11), Hay Head (2), Ledbury (9), Malvern (7), 

 Wenlock (5), Coalbrookdale (4), Walsall (1), Eastnor (2), Usk (2), and Cardiff (1); 

 in the Lower Ludlow of Ledbury (4) and Trecastle (2); and from the Upper Ludlow 

 of Much Marcle, there is a specimen in Dr. Grindrod's collection, which may be this 

 or an 0. ibex. I have also seen four examples from the Upper Silurian rocks of 

 Kerry, but have not met with it as a Scotch fossil. 



In addition to these, the species has been recorded by Murchison from the Bala 

 Beds at Llandovery ; by M'Coy from Coniston Limestone ; by Salter from the Upper 

 Llandovery of Craig Nir ; by Dixon, from the Woolhope Limestone, Scutterdine ; 

 by Murchison, from Upper Silurian, Presteign ; by Phillips, from Haverfordwest, 

 Llandeilo, and Abberley ; by Sedgwick, from the Denbigh Flags ; by Salter, from 

 the Woolhope Limestone of Barr, from the Lower Ludlow of Parkes Hall, and 

 from Upper Silurian of Croagh-Martin ; and by Harkness, from the Balmae Schists, 

 Kirkcudbright. 



Out of the British Isles, this species is recorded by Eichwald from the Lower 

 Silurian of Russia, and by Schmidt from the Upper Silurian of the same country. 

 In Sweden it has long been known by Hisinger's figures, as an Upper Silurian 

 fossil. Barrande finds it widely spread throughout his third fauna, it being about 

 the only Bohemian species he admits to be identical with those of any other country. 

 It is recorded also by Hall, from the Niagara and Clinton groups of New York ; and 

 from the former group in Wisconsin and Illinois. It is thus the most widely distri- 

 buted Silurian Cephalopod both in time and space. 



Orthoceras Duponti, Barrande, PI. V. figs. 1, la, 2, 2a. 



1868. Orthoceras Duponti, Barrande, ' Syst. Sil. de Boheme,' pi. 285, &c, p. 324. 

 Syn. 1873. Orthoceras subannulare, Salter, ' Camb. and Sil. Fossils,' p. 98. 



Type. — The section is circular and the shell always straight. The rate of 

 increase is 1 in 10. The body-chamber is 4 times the length of its basal diameter. 



