﻿BRITISH FOSSIL CEPHALOPODA. 97 



observations do not enable me to separate them. Small examples of this species 

 do not show the crinoid aspect of 0. kendalense, and they are therefore considered 

 distinct. The observation of the fact that Sowerby's type has transverse lines rids 

 us of much difficulty in the discrimination of this and allied species. 



Distribution. — Examples have been examined from the Wenlock Shale, Dinas 

 Bran (1) ; from the Coniston Grit, Howgill Fell (2) ; from the Lower Ludlow 

 of Ledbury (2), Mocktree (1), and Shelderton (1) ; from the Upper Ludlow of 

 Benson Knot (5), Kendal (1), Ledbury (2, one of which shows the contracting 

 body-chamber, and the other the loss of ribs), Malvern (7), of Ludlow (3), of 

 Builth (1), and of Usk (4). Sowerby's 0. articulatum, which I have not seen, is from 

 the Upper Ludlow, near Aymestry. An external cast, with the ornaments of this 

 species rather exaggerated, but with a rate of increase in the apparently uncom- 

 pressed shell of 1 in 6, and with an elliptic section, occurs in the Lower Silurian rocks 

 of Waterford ; another in Tipperary, and a doubtful form in the May Hill Sandstone. 

 Some of these may, perhaps, belong to 0. Grayi, or to some species as yet undefined. 



Specimens referred to this, but of which there are no means of knowing whether 

 this species, 0. tenuiannulatum, or 0. tracheale are intended, are recorded by Phillips 

 from the Wenlock Shale of Llandeilo, May Hill, Woolhope, and Abberley ; by Lap- 

 worth from the Wrae Limestone and Riccarton Beds ; in the Catalogue of Western 

 Scottish Fossils from Ardmillan Braes ; by Sedgwick from Upper Ireleth Slates, 

 Howgill, and from the Coniston Grits; by Strickland from the Upper Ludlow of 

 Hagley, and by Salter from the same at Coalbrookdale. Other references under this 

 head are either obviously to longitudinally ornamented species, or to examples in 

 Lower Silurian rocks, in which this has not as yet been proved to occur. On the 

 Continent it occurs, of course, in Gothland. 



Orthoceras tracheale, Sowerby, PI. Y. fig. 7. 



1838. Orthoceras tracheale, Sowerby iu Murchison's ' Silurian Syst.' pi. 3, fig. 96. 

 1851. „ „ M'Coy, ' Pal. Foss.' p. 321. 



1854. „ „ Salter in Murchison's ' Siluria,' pi. 34, fig. 6. 



Query 1848. Orthoceras perelegans (part), Salter, ' Mem. Geol. Survey,' vol. ii. pi. 13, figs. 2, S 

 (not fig. 4). 



Type. — The specimen figured by Sowerby is merely a short hollow cast in 

 the usual Tilestone flag. It shows that the section was nearly circular, and the 

 increase probably slow. The ornaments would be acute, scarcely separate, nearly 

 direct ribs, f- the diameter apart. These are covered by parallel sharp riblets. The 

 septal surface at the end is rather flat. From the Tilestone of Horeb Chapel, 

 Trecastle. In the Collection of the Geological Society. 



General Description. — The section in well-preserved exanxples (fig. 7) is circular, 



o 



