Description of the Fossils in the older Deposits of the Rhenish Provinces. 347 



lower angles formed by the fracture of the same band an oblique ellipsis is obtained whose greater 

 axis corresponds with a line passed through the siphon. Septa nearly flat and somewhat oblique. 

 Siphon small, nearer to the centre than the edge. 

 This species is distinguished from all its congeners by the remarkable colours with which it is orna- 

 mented, as well as by their arrangement. This circumstance, together with several other considerations, 

 has a tendency to prove the Orthoceratites to have been external and not internal shells like the 

 Selemnites. 



PafFrath; very rare. 



11. Orthoceratites nodulosus, Schlot. Petrefact., PI. XI. f. 2. Tab. nost., XXXI. f. 4-, 4 a. 



We have given a new representation of this species, as Schlotheim's figure does not clearly show the 

 characters. It might even be taken for a different shell, for the drawing exhibits a very large siphon 

 placed between the centre and the edge, while it is in reality central and small. Moreover the section 

 of the shell appears to be elliptical instead of being exactly circular. 



Eifel. 



12. Orthoceratites triangularis, nob., Tab. nost., XXVII. f. 1, 1 a. 



Shell in the form of an extremely elongated triangular pyramid, of which the section is a rectangular 

 isosceles triangle with rounded angles, whose two smaller sides are curvilinear, but the larger or 

 hypothenuse is straight, whence it results that the small faces of the pyramid are curved, but the 

 large face flat. Notwithstanding the absence of the shell, there may still be observed fine, irregular, 

 slightly prominent striae, which upon each of the lateral faces rise toward the dorsal keel, forming 

 with the suture of the septa an angle of 45°, and then pass over the ventral face, where they de- 

 scribe a curve whose convexity seems tui'ned toward the summit. Septa triangular, rounded, concave, 

 with slightly undulated edges, the latter turning forward a little upon each angle or keel, then turn 

 backward again in passing over the face. Height of the chambers variable, but they are generally 

 very low, as eighteen may be counted in a space equal to the width of one of the smaller sides. 

 Siphon circular, rather large, placed against the middle of the larger side and opposite to the right 

 angle of the pyramid. 

 This gigantic species was at least two metres in length ; the fragment we possess, and which could not 

 be figured entire, measures 0*36. We have seen at Wurzbourg, in possession of Professor Landaberger, 

 a specimen of this Orthoceratite, upon which are wide, rounded, slightly raised folds, corresponding to 

 swellings or nodosities, placed upon the principal keel : in the specimen which we have represented there 

 are only slight indications of these folds, which must undoubtedly be more prominent toward the summit 

 of the shell than at the anterior part, the only portion which we have. 

 Wissenbach ; very rare. 



13. Orthoceratites subfusiformis, MUnst., Gomphoceras Beit. z. Petref., iii. Heft, PL XX. f. 6, 7. Tab. 

 nost., XXVIII. f. 2, 2 a. 



We refer to this species a shell from Oberscheld, which at least comes very near to it. Nevertheless, 

 it is rather conoidal than ventricose ; in which it resembles the O. fusiformis of Min. Conch,, Tab. 

 DLXXXVIII. f. 1 and 2. The shell is rather thick and covered with fine close-set striae, turning toward 

 the place of the siphon, which is submarginal. The presence of striae upon this shell, which Count 

 MUnster describes as being smooth, has decided us to give a new figure of it. 



Oberscheld ; rare. 



14. Orthoceratites subpyriformis, MUnst., lac. cit. supra, PI. XX. f. 10. Tab. nost., XXVIII. f. 3, 3 a. 

 Shell regularly pyriform, short, smooth, and rounded anteriorly. Aperture narrow, transverse, having 



at the ventral part a deep, symmetrical, and rounded notch. Septa straight, horizontal, numerous. 



