123 

 longitudinal sulcus, and others have been seen with two ; but what has 



j 



been the use of these sulci is not known. 



So perplexed were the earlier writers on this fossil, respecting its 

 nature and origin, that they were even puzzled to ascertain under which 

 of the natural kingdoms to place it. Not only the earliest writers on 

 mineralogy considered it as originally belonging to the mineral kingdom, 

 but even Woodward supposed it to be a stone, sui generis. Langius 

 considered it as a stalactite; Libavius believed it to be indurated 

 amber ; and even Mr. de Costa supposed it to be a natural fossil, or lapis 

 sui generis, composed of talc and spar, and compared its cavity to that of 

 stalactites; adding " As for that marine body, the alveolus, I cannot 

 think otherwise than it is of the Nautilus kind, which, at the concre- 

 tion or formation of the belemnites, became accidentally lodged in its 

 cavity, in the same manner as all other marine bodies, became lodged 

 in the various fossil substances we now find them in." Phil. Trans. 

 1747. Stobaeus and Hellwing were of opinion that it was of vegetable 

 origin. 



Among those who conceived it to be of animal origin, we find no 

 small discordance of opinion; some believing it to have been the horn, 

 and others the tooth, of an animal. Of those who entertained the lat- 

 ter opinion, some supposed it to be the tooth of a crocodile, and others 

 of a physeter; Lhwydd believing it to be the tooth of a particular spe- 

 cies of the whale, resembling the narwhal. Some were of opinion that 

 it was the spine of a particular species of echinus. M. Titius conjectured 

 it to be one of the extremities of a species of Stella marina. M. de 

 la Tourette believed it to have been a species of Polype; and Waller and 

 others a species of Holothuria. 



Later oryctologists, particularly Rosinus, Erhart, Breyn, Klein, and 

 Linnaeus, have agreed, that this body must be considered as the remains 

 of the chambered shell of a marine animal, the recent analogue of 

 which is unknown. With this opinion M, Walch perfectly agrees, 

 believing it to be supported by the circumstance of the nacre having 



