78 



Proceedings of tloc Royal Physical Society. 



gested by their author. For instance, I see no reason why 

 Loxoccras * should not be employed for those Orthoceratites 

 with an oval section, the septa waved and placed obliquely 

 with respect to the axis of the shell, and an eccentric si- 

 phuncle. This section is typified by the 0. Brcynii (Martin, 

 sp.), a species met with in Scotland. Again Cycloceras-f 

 was intended for conical forms marked with prominent con- 

 centric rings, and a dorsal siphuncle. The type of this division 

 is again a Scotch fossil, Orthoceras annulare (Fleming). M. 

 A. D'Orbigny established a genus under the name of AjAo- 

 ceras\ for certain Carboniferous Cephalopods, with a horn- 

 shaped shell, and a subcentral siphon. Amongst these he 

 introduced the Orthoceras clentaloicleum (Phill.),§ which has 

 been found at the South Hill, Campsie.ll I have examined the 

 figured type specimen of this species, and I find it to -be most 

 unquestionably a Dentalium, possessing all the characters of 

 the Carboniferous forms of that genus. The late Professor 

 Fleming described two Orthoceratites, 0. unclatiini and 0. 

 sulcatum, which appear to be identical ; the former is said 

 to have the annular ridges of the shell waved and smooth, 

 the latter waved and striated, but specimens have come 

 under my observation in which both these characters were 

 combined. 



The latest arrangement of the Carboniferous Orthoceratites 

 is that of Professor de Koninclv,1[ who aives the following- 



general classification :- 



Orthoceras. 



Group I. — Siplion cylindroid — 



1st. Lcevia, surface smootli, or 

 nearly so. 

 (t. Gracilia. 

 h. Rc(jularia. 

 2il. Annulata, surface with 



wrinkles or concentric rings. 

 3d. LincfUa, surface with strire 

 or longitudinal ridcres. 



Group II. — Siphon numuiuloid — 

 l.st. NuimniUaria, surface 

 smooth, or nearly so. 



2d . Moniliformia, surface striateil 

 longitudinally. 



* Synop. Carh. Lime. Foss., 1811, p. 6. f Ibid. 



X Prodrome de Pal., i., p. 112. 



§ Geol. Yorkshire, 1836, ii., p. 230, t. 21, f. 12. 



Il W. Scot. Fossils, p. 59. 



If Faune du Calc. Carbonif. de la iJelgiquo, 1880, pt. 2, p. 50. 



