142 



transverse ridges, which bifurcate at their origin: a deep rounded 

 groove seeming to terminate the first whirl. A similar termination of 

 the first whirl is observable in the fossil, Fig. 10, to which fossil it 

 somewhat approximates. 



Different opinions have been entertained with respect to the ammo- 

 nites assuming naturally an oval shape. Whilst this has been said to be 

 the case by some, who have adduced specimens of this fossil in this form,, 

 in proof of their assertions, others have contended, that the oval figure 

 has proceeded from compression. The only specimen in this form, which; 

 I for some time possessed, was entirely pyritous ; and by observing that 

 a part of the specimen retained the appearance and proportions of a 

 round specimen, I hesitated at admitting the proof of the fact, from 

 that instance. Since then, I have seen oval specimens, indubitably 

 possessing their original form, from Wiltshire ; and have lately obtained 

 one myself from Steyning, which is represented Plate IX. Fig. 6, and 

 proves, undoubtedly, that shells of this genus existed originally in this 

 shape. 



LXXVIII. Baculites. A straight, cylindrical, or slightly conical 

 shell, divided into chambers by transverse, sinuous, and imperforated 

 septa; the articulations, or sutures, being indented in the manner of the 

 battlements of a tower. 



The fossil, the characteristics of which are here given, was found by 

 Faujas St. Fond, among the fossils of St. Peter's Mountain, and was by 

 him considered as a straight Cornu ammonis. Histoire Naturelle de la Mont, 

 de St. Pierre, p. 140. The propriety of forming with it a distinct genus, 

 as Lamarck has done, is obvious; since, on the same principle that 

 St. Fond would name it Ammonites rectus, we ought to place the ortho- 

 ceratites under the genus Nautilus, and name it Nautilus rectus, as has. 

 been done by Baron le Hupsch, who has given a figure of this fossil 

 (Baculites) accompanied with observations on its structure, and on the 

 relationship which it bears to the Cornu ammonis. Nouvelles Dccouvertes 

 de quelques Testacees Petrifies rarcs et inconnus, pour servir a, I Histoire Na-. 



