﻿B. Etheridge, Jim. — Contributions to British Palceontology. 249 



Class Cephalopoda. Genus Orthooeras, Breyn. 



Orthoceras Brownianun, p. nov. Plate XII. Figs. 15a and 156. 



Stiletlo-like Orthoceras, Rev. T. Brown. Trans. R. Soc. Edinb., vol. xxii. pt. 2, p. 362. 



(Compare 0. calamus, de Kon., Descrip. Anim. Foss. Terr. Carb. Belgique, 

 p. 506, Supplement, p. 703, pi. 59, f. 2 a-d ; 0. regulare, v. Schl. Sandberger's 

 Die Verstein. d. Rhein. Schichtensystems in Nassau, 1856, p. 173, atlas, pi. 20, 

 f . 2 ; 0. planiseptatum, Sandb. loc. cit., p. 160, atlas, pi. 17, f . 4 ; 0. acutissimuin, 

 id. loc. cit. p. 173, atlas, pi. 20, f. 10.) 



8p. Chars. — Shell much elongated, pointed, and stiletto-like, 

 tapering very gradually; section at the smaller end circular (not 

 determinable at the larger end). Septal sutures distant as compared 

 with the diameter of the shell, horizontal, not waved ; intervals 

 decreasing very slightly towards the smaller end ; septa, as denoted 

 by the only one visible, somewhat flattened, not very convex. 

 Chambers as denoted by the intervals between the septal sutures, 

 with the height (vertical) exceeding the diameter (transverse). 

 Siphuncle subcentral. The specimen where septate is a fraction 

 more than two inches long ; the diameter of the smaller end is as 

 near as possible a little less than half a line ; at the upper end 

 . immediately before the point where it is crushed the diameter is 

 about one line and a half. In the space of one inch there are 19 

 or 20 chambers. Surface smooth. 



Ohs. — For an introduction to this elegant Orthoceras we are in- 

 debted to the Eev. T. Brown, M.A., who aptly termed it in his 

 paper "On the Mountain Limestone and Lower Carboniferous Rocks 

 of the Fifeshire Coast," etc.,' the " thin stiletto-like Orthoceras," 

 and mentions it as exceedingly characteristic of his Bed F, or 

 " Ardross Limestone," near Elie. 



In Prof, de Koninck's classification of Carboniferous Orthoeeratiies 

 this species would clearly come under the division " Orthocerata 

 gracilia,'" and in form and slenderness resembles the typical species 

 of that section, 0. Martinianum, de Kon.,^ but the septa are rather 

 distant and cannot be described as very close, as in the Professor's 

 species. There is a closer resemblance to his 0. calamus ; especially 

 to the apical portion represented by Fig. 26 on the 59th plate of 

 the "Animaux Fossiles." Our form appears to taper at nearly the 

 same ratio, but is perhaps thinner and more slender ; the septal 

 sutures are about the same distance apart as those of 0. calamus, 

 and the section is equally circular, but the siphuncle is subcentral 

 in position. 



I would also call attention to the resemblance of this Orthoceratite 

 to the apical portion of 0. regulare, v. Schlotheim, as figured by the 

 Drs. Sandberger, but in this case the septa certainly appear too far 

 apart, and, as in the case of Prof, de Koninck's species, the siphuncle 

 is central. 0. Broionianum is also not unlike the apical portion of 

 0. planiseptatum, Sandberger, but here the chambers are far too broad 

 for their height to bear close comparison with the present form. In 

 all these cases it must of course be borne in mind tlaat no comparison 

 can be made with the large upper ends in the three species, 0. cala- 

 mus, 0. regulare, and 0. planiseptatum, especially in the two latter. 

 ^ loc. cit. supra. 2 ^^^ qH^ supra, p. 605, t. 44, f, 4. 



