﻿148 BRITISH FOSSIL CEPHALOPODA. 



noted under that species, the flatness and greater closeness of the septa, as well 

 as other differences, easily distinguished them. They may, however, belong to 

 O.pictum. Portlock referred the same to 0. cylindraeeum and 0. incequiseptum of 

 the Carboniferous rocks, but the former has not such close septa, and shows pecu- 

 liarities in youth, and the latter has a more rapid rate of increase. The close septa 

 separate the species from 0. regular e and 0. speciosum, to which I think some Irish 

 specimens have been referred. It is very probable that the specimens quoted as 

 0. conicum (Hisinger, but not Sowerby) belong here. I can find no feature which 

 distinguishes this from 0. novellum, as figured and described by Barrande. 



Distribution. — In the Bala Series of Kildare (11), of Bala (1), of Marshbrook (1), 

 of Horderley (2), and Barking Dent (1) ; in the Lower Silurian of Egool (1), and 

 Desertcreat? (I); in the Lower Llandovery of Blaen-y-cwm (1), and near Cheny 

 Longville (1); in the Upper Llandovery of Tortworth (1); in the Wenlock 

 Series of Usk (1) and Montgomery (1) ; in the Lower Ludlow of Ludlow (4) and 

 of Presteign (3). 



It is also recorded by Portlock from the Lower Silurian of Tyrone ; by Kelly 

 from the same horizon at Tullyconnor, Tonlegee, &c. ; by Brown and Henderson from 

 the Upper Silurians of the Pentlands, and by Strickland from Upper Ludlow, Hagley. 



Orthoceras prim^evum, Forbes, PI. XVII. fig. 4. 



1845. Criseis prim^va, Forbes, ' Quart. Journ. Geol. Soc' vol. i. p. 146. 



1846. „ „ Sharpe, 'Quart. Journ. Geol. Soc' vol. ii. pi. 13, fig. 2. 

 1852. Orthoceras prim^evum, M'Coy, 'Pal. Foss.' p. 316. 



1852. „ „ Salter, Appendix A to M'Coy's ' Pal. Foss.' p. viii. 



1857. „ „ Salter in Murchison's ' Siluria,' Foss. gr. 62, fig. 4. 



1873. „ „ Salter, ' Camb. and Silurian Foss.' pp. 97, 159. 



Syn. 1846. Criseis ventricosa, Sharpe, loc. cit., pi. 13, fig. 3. 



1852. Orthoceras ventricosum, M'Coy, ' Pal. Foss.' p. 318. 

 1852. „ „ Salter in App. A to 'Pal. Foss.' p. vii. 



1873. „ „ Salter, ' Camb. and Sil. Foss.' pp. 98, 159. 



Query 1843. Orthoceras regulare, Portlock (in part), 'Geol. Eep.' p. 376. 

 1852. „ torquatum, Salter, App. A to ' Pal. Foss.' p. vii. 



1873. „ „ Salter, ' Camb. and Sil. Foss.' p. 187. 



Type. — This is probably an example in the Woodwardian Museum referred to 

 as b. 544 in Salter's Catalogue. It is a flattened specimen, giving no data except 

 as to its rate of increase. This is 1 in 11 in the flattened impression. No signs 

 of any ornaments are visible, and there are longitudinal cracks due entirely to 

 breaking. The specimen commences at -§ inch diameter, and tapers nearly to a 

 point in 7£ inches. It is from the Denbigh Flags. 



General Description. — These flattened impressions on shale are very common, 

 and have undoubtedly been proved to belong to Orthocerata by the discovery 



