ORYCTOLOGY. 



be obvious, must be exceedingly numer- 

 ous : Scheuchzer was able to determine 

 the existence of one hundred and forty- 

 nine species. The difference of size ob- 

 servable in these fossils is not less re- 

 markable than the variety of their forms, 

 some being found not much larger than 

 the head of a pin, whilst oihers have been 

 found as large as the top of a small table. 



A peculiar appearance is observable on 

 the surface of many of these fossils, which 

 depends on the peculiar form of the septa 

 which separate the chambers ot the shell. 

 These septa in the nautili are smooth, and 

 terminate at the surface of the shell in a 

 straight line ; but in the Cornua Ammonis 

 they become undulated as they extend 

 outwardly ; and in some so much so as to 

 form, on the outer surface, deeply crenu- 

 lated lines, giving the appearance of folia- 

 ceous sutures. When the cavities of the 

 shell have become filled with stone, and 

 the septa just mentioned have been re- 

 moved, as is frequently the case, by some 

 chemical agent, ihe casts formed in the 

 chambers separate, each forming a curi- 

 ously figured stone ; these separate casts 

 have been termed spondilolites. (Plate 

 II. fig. 4.) By the junction of these are 

 formed the foliaceous sutures above-men- 

 tioned. The Cornua Ammonis were for- 

 merly called serpent-stones ; the appear- 

 ance which they yield of a serpent coiled 

 having led the vulgar to consider them as 

 petrified serpents. 



The fossil Cones are very few when 

 compared with the numerous species 

 known in a recent state ; the same may 

 be also said of the Cypreae. In both these 

 genera the species are mostly made out 

 more from the colour and the markings of 

 the shells, than from the peculiarities of 

 their form ; but in the fossil shells the co- 

 lours no longer exist, and of course the 

 species in these can very seldom be pre- 

 sumed. The fossil Volutes, as far as can 

 be judged from their form alone, differ 

 generally from the recent species. With 

 respect to the genus Buccinum, Strombus, 

 and Murex, the number of species of the 

 fossil shells do not appear to equal those 

 which are known in a recent state. This is 

 the case also, in a still greater degree, 

 with the genus Trochus. The fossil shells 

 of the genus Turbo are pretty numerous, 

 and some of them very closely resemble 

 those of known recent species. One fos- 

 sil shell of this genus is very remarkable 

 for its vast size, being upwards of a foot 

 in length. The cast of another species is 

 so large as to weigh four or five pounds. 

 Nothing like this occurs with respect to 



the species of the genus Helix : the fossil 

 shells of this genus very much resemble 

 those which are recent, and are not found 

 of any considerable magnitude. The fos- 

 sil shells of the genus Nerita by no means 

 display so many species as the recent ; 

 but some of the fossil species far exceed 

 the recent in size, and one in particular is 

 twelve times the size of any known recent 

 species. Of the genus Haliotis, it is not 

 positively determined that a single shell 

 has been seen, which could be considered 

 as fossil. Fossil shells of the genus Pa- 

 telta are by no means common. Several 

 species have, however, been found in 

 France, in a state of excellent preserva- 

 tion. Some few also have been found in 

 the cliffs at Harwich, and others, of a dif- 

 ferent species, imbedded in the lime-stone 

 of Gloucestershire. Dentalia, apparently 

 similar to existing species, have been 

 found in Hampshire, and in some parts of 

 France and Italy, exceedingly well pre- 

 served. In Italy, also, have been found 

 specimens of Serpulae, very similar to 

 those which are known recent ; but others 

 have been found in France exceedingly 

 different from any known recent species. 



The Orthoceratites, a lapidified conical 

 or cylindrical chambered shell, the septa 

 dividing the chambers of which are perfo- 

 rated like those of the Nautilus, is a ge- 

 nus of which not a species is known in a 

 recent state, excepting the microscopic 

 specimens found by Plaucus in the sand 

 of the Riminian shore. Much is wanting 

 to complete the history of this fossil, since 

 from the state in which the specimens 

 have in general been found, very few, or 

 perhaps none, have been obtained perfect. 

 Authors have divided them into those 

 which are straight (Plate II. fig. 8.), and 

 those which have a spiral termination, the 

 latter of which are considered as fossil 

 shells of the Nautilus lituus ; but the ex- 

 traordinary disparity of size is sufficient to 

 shew that they can hardly be considered 

 of the same species, the recent shell being 

 seldom more than an inch in length, 

 whilst the fossil is described as being 

 sometimes the size of a man's arm. 



The Belemnite (Plate II. fig. 7.) is a spa- 

 those radiated stone, generally conical, 

 but sometimes possessing a fusiform fi- 

 gure, and contains, in an appropriate cavi- 

 ty at its larger end, a smaller calcareous 

 body (alveolus) which has evidently been 

 a concamerated shell, the septse of which 

 are pierced like those of the preceding 

 fossil. These fossite are from an eighth 

 of an inch to two inches in thickness, and 

 from an inch to a foot and a half in length. 



