Description of the Fossils in the older Deposits of the Rhenish Provinces. 345 



position of its siphon ; and in its form being a less elongated cone. According to Count Miinster it is 

 distino-uished from O. venustus in being less conical, and in its more marginal siphon ; the siphon of O. 

 venustus being nearer to the centre than to the edge. Although we have given to this shell the name of 

 O. gracilis, like other authors, it is still very doubtful if it be the same as that figured by Blumenbach. 

 In the latter the siphon is marginal, the septa are more distant, and the whole shell much more elongated, 

 since the author says it is cylindrical and not conical. 

 Wissenbach ; very common. 



3. Orthoceratites Wissenbachii, nob.. Tab. nost., XXVII. f. 3. 



Shell elongated, cone-shaped, smooth anteriorly, annulated toward the summit by transverse ridges, 

 more prominent and undulated as they become nearer to it. The position of these ridges is incon- 

 stant. Sometimes there is only one placed at a distance equal to two successive septa ; sometimes 

 they form two varices adjoining the suture of the septa. The latter are straight, horizontal, and 

 slightly concave. Siphon small, round, quite marginal, and apparently continuous. Chambers 

 numerous, shallow ; two or two and a half to a diameter. 

 In the position of the siphon the O. Wissenbachii approaches to the O. Steinhaueri of Sowerby, from 

 which, however, it is distinguished by its other characters. The disposition of the rings recalls to mind 

 also the O. duplicatus of Miinster, but this latter has the siphon central. 



Var. a. This shell differs from the preceding in being smooth and destitute of rings throughout its 

 len<^th, and further because the septa are much closer, since five may be counted in the space of one 

 diameter. As to the obliquity of the septa, in our specimens it appears to be the result of accidental 

 compression. When this variety shall have been more fully studied, it will probably constitute a distinct 

 species. 



Wissenbach ; rare. 



4. Orthoceratites striolatus, H. v. Meyer, bei Dechen's Handb. der Geogn. von De la Beche, p. 536. 



O.fragilis, Coll. of Schl. Jahrb. f. Min. 1833, p. 483. Tab. nost., XXVII. f. 5, 5 a. 

 Shell of an acute cone shape, entirely covered with numerous filiform unequal stride, undulated in 

 places. Septa horizontal, near together ; (two in the height of one diameter). The siphon, ill pre- 

 served in our crushed specimens, appears to be submarginal. 

 This species differs from the O, cinctus of Miinster, in its more conical form, its less regular striae, and 

 probably also in the position of the striae. It has some analogy with O. cincta, of Min. Conch., PI. 

 DLXXXVIII. f. 3, and O. centralis, of Hisinger, Leth. Suec, Tab. IX. f. 4, which, like Count Munsters, 

 have the siphon central and the striae equal, with very regular interspaces. Neither does the O. striolaris 

 appear to us to attain the dimensions of the shells represented and described by these authors and by Phillips. 

 From Herborn, in the Posidonia slates; common. 



5. Orthoceratites linearis, Miinst, Beitr. z. Petref. iii. Heft, PI. XIX. f. 1. 



This species differs from the O. cinctus of the same author, and also from the O. cincta of Min. Conch., 

 arid the O. centralis of Hisinger, in the fineness of its striae, which appear to be more distinct in young 

 individuals or toward the summit of the shell. 



Elbersreuth, Oberscheld ; common. 



6. Orthoceratites scalaris, Goldf., Bonn Museum. 



This shell, of which we possess only an impression, and which we have seen in the same condition in 

 the Museum of Bonn, is conoidal and very short. Its diameter increases rapidly. It is ornamented with 

 horizontal transverse rings of which the breadth is equal to half the smooth space which separates them. 



Herborn in the Posidonia slates ; rare. 



7. Orthoceratites Dannenbergii, nob.. Tab. nost., XXVIII. f. 1, 1 a. 



Shell subcylindrical, forming a very elongated cone, covered with rounded, slightly prominent, regular, 



