“ANMMONITES. CEPHALOPODA. T5 
mon’s Horn; Jupiter being worshipped by the Egyptians, under the name of 
Ammon, a deity, represented by the ram. The whole of the ancient seulp- 
tural representations of Jupiter, having invariably ram’s-horns, as are also 
those of Alexander the Great after he was deified, as the son of Ammon. 
A superstitious belief prevails in England, that Ammonites are petrified 
snakes, founded, no doubt, upon a legend in Camden’s Britannia, which is 
thus recorded. ‘* Upon the same river Avon, which is the boundary here 
between this county (Somersetshire) and Gloucestershire, on the western 
banks of it, is Cainsham, (now Keynsham,) so termed from Keina, a devout 
British virgin, whom mary of the last age, through an over credulous temper, 
believed to have changed serpents into stones, because they find sometimes in 
quarries some such little miracles of sporting nature. And I have seen a 
stone brought from thence, winded round like a serpent, the head whereof, 
though but imperfect, jutted out in the circumference, and the end of the 
tail was in the centre, but most of them want the head.” 
This is a most comprehensive genus, consisting of shells found only in a 
fossil condition. It is a remarkable circumstance, that not a single type of 
this extensive family exist in the present seas of our globe. In Great Britain 
and Ireland alone, 184 species have been ascertained and figured.* They 
occur in all formations from the Transition strata, and disappear with the 
termination of the Chalk. Besides those which are met with in the strata of 
Britain, there are numerous other species differing entirely from them, which 
occur in various quarters of the globe. .M. Brochart has enumerated two 
hundred and seventy species. These Ammonites differ according to the age 
of the strata in which they are imbedded, and vary in size from an eighth 
of an inch to more than four feet in diameter. One of the earliest forms 
of this genus, is the A. Henslowi; (now Goniatites Henslowi,) plate I. fig. 6. 
which is lost with the Transition series. The A. Nodosus, plate III. fig. 27. is 
peculiar to the Muschelkalk.' Other Ammonites appear only in a certain 
definite strata of the Cretaceous or Oolitic formations. 4. Bucklandi, plate 
III. fig. 28, occurs only in the Lias, while A Goodhaili, plate III. fig. 37, is 
peculiar to the Greensand, and A, rusticus, plate III. fig. 38. is met with only 
in the chalk. There are no single species which runs through the secondary 
periods, or which have passed into the Secondary from the Transition 
formations. 
Mr Phillips gives the following distribution of Ammonites through the 
various geological formations. None have been found in the Tertiary series ; 
in the Cretaceous series, 45 ; in the Oolitic series, 137 ; in the Saliferous series, 
15; in the Carboniferous series, 7; and in the primary, or those strata which 
are included in the lower regions of the Transition series, 17; making a total of 
223 species. These he divides into sections, or sub-genera. ‘‘ It is easy to 
see,” says he ‘‘ how important in questions concerning the relative antiquity of 
stratified rocks, is a knowledge of Ammonites, since whole sections of them 
are characteristic of certain systems of rocks.” + But recent discovery has con- 
siderably increased those numbers. 
~ The shells of this genus have greatly perplexed conchologists and geologists ; 
as they have never been able to account for their use and plan. Impressed by 
the analogies presented by the genus Spirula, plate III. fig. 18, (a genus known 
only in a recent state,) Lamarck and Cuvier considered them to be internal 
shells ;- that is, enveloped within the body of the animal. Cuvier was led to 
* See Brown’s Mlustrations of the Fossil Conchology of Great Britain and Ireland, 
plates 4 to 20.+ 
+ Philip’s Guide to Geology, 1834, section 82. 
