The Ammonite above mentioned is among the most in teresting of all the fossil shells, as well for the beauty and variety of the species, as for the immense quantity in which it is found, and from its universality in the series of strata. These are the serpents, or petrified snakes of the common people ; and from their forms also have been de rived volutes for fanciful orders in architecture. In other respects, they are interesting, as having been introduced into the ancient mythology of Egypt, and hence transfer red to the Jupiter Ammon, the mixed divinity of Greece and Egypt. On the coins of Alexander they are found for the same reason ; nor is it wonderful that they had equally attracted the attention of the ancient naturalists and geographers, by whom they are mentioned. In some parts of Somersctshire, where they abound, as at Wokey, where they are of great size and beauty, the country peo ple use them with great taste in building or ornamenting their rustic cottages. While the quantity of these fossils is considerable, the species are also very numerous, up wards of 300 distinct ones having been ascertained. The variations that form these, are produced by the different dispositions and forms of the stria, in the first place, which are shallow, or deep, or wide, or narrow, or simple, or bifurcated, or trifurcated, or straight, or undulated. Other differences consist in tubercles or similar orna ments ; and all these, being found in different parts of the shell, produce many distinct characters, by their various dispositions and combinations, while an additional set of marks are found in the intricate labyrinthine ornaments painted or indented on the surface, often resembling su tures. This, also, like the former, is a concamerated furnished with a siphunculus ; and as separate stony con cretions are sometimes produced in the chambers, these have been called spondylolites. They are often hollow, and beautifully crystallized with coverings of calcareous spar. These shells are often remarkable for their pearly coating within ; which is, in some cases, not only per fectly preserved, but exceedingly brilliant and various in the colours. It is to this shell that the celebrated fire marble of Carinthia owes its beauty. It is not uncommon for the ammonites to be flattened by compression in the strata.
The Baculite is analogous to the ammonite in its cellu lar structure, and was once called a straight ammonite, hut is now very properly distinguished. It bears the same analogy to these as the orthoceratite does to the nautilite. It is a rare fossil, and no existing species are known. The Hamite is similar in general structure, but has no siphun culus, and is a curved shell. It is also rare, but occurs in the green sand stratum in Wiltshire, and elsewhere. The Scaphite is an analogous genus, separated from the former by Mr. Parkinson, on account of the peculiar dis position of its spiral cells.
Turrilites is another of these multilocular shells, but in this all the cells are visible in the form of the external spiral. It is rare, and the species are few. The Nummu lite is also a chambered shell, of a flattened form, which has often been mistaken for seeds of plants, and even for money, being known to the ancient naturalists. It abounds in Egypt, and aids in the construction of the Pyramids. The species are all small, and sometimes very minute, but they are numerous, while the quantity of this genus that occurs in calcareous strata is also very great. In the Fas
ciolite, the concamerations are tuberal and spiral, and it is somewhat akin to the preceding genus. It is not nu merous. We need only mention the names of the other genera, Rotalitcs, Lenticulina, Lituola, Spirolina, 1\Iiliola, Renulina, and Gyrogouites, all of an analogous structure to the preceding, and some of them very abundant, though the greater number are extremely minute. Some do not exceed the head of a pin in dimensions.
The bivalve shells form an immense tribe among the fossils ; but we can only notice some of the most promi nent, reserving the name of the genera to our list at the end of this section.
The Pinnite is rather rare, but it occurs in the English oolites. Pectunculus is rather abundant in England. Tri gonia is remarkable for its extraordinary shape, and it con tains a considerable number of species. The Teredo is also interesting, from its being sometimes found in the very wood in which it lived, both of them being petrified. Ostrea is a very abundant genus, and about twenty distinct species have been ascertained. The most remarkable of of these is that found in Switzerland, the shell of which is sometimes more than two inches thick. In England, some of the species form immense banks. The Terebratula is also a common fossil ; and, in the Scottish strata, where these bodies are comparatively rare, it becomes therefore of interest. It is found in the limestones of Arran, and elsewhere. But as our limits will not permit us to do more, we shall now give a list of the genera which have been found fossil, omitting any notice of species, partly on account of the room which they would occupy here to very little purpose, and partly because that list is as yet imper fect; a great number of distinct fossils still waiting until better preserved specimens shall allow conchologists to place. them under specific names in the arrangement. It will here be convenient to the reader that we should com mence from the zoophytes.
Of Fossil Fishes.
Fishes in a fossil state exist in many parts of the world, but the greatest number, and in the most perfect preser vation, occur in Italy ; and in that country, Monte Bolca is the celebrated repository. The mode in which these specimens become imbedded will form an object of consi deration hereafter. Near the lake of Constance, at Pap penheim, and Oeningen, they are also found in considerable abundance, and in good preservation ; as they are at Aix in Provence, at Montmartre, and in several parts of Eng land, as in Oxfordshire, Dorsetshire, Leicestershire, Gloucestershire, Lincolnshire, and Kent.
Those of Switzerland occur in a series of beds, consisting of sandstone, argillaceous marl, foliated marl slate some what bituminous, and of two or three distinct characters, and limestone, in which the fish are found, together with some fragments of insects, amphibia, and leaves. There can be little reason to doubt that this is a fresh-water for mation, and that the fish were the inhabitants of an inland lake. Near Paris these fossils are found in the fresh-water basin, and in that which is called the lowest fresh-water bed ; whence these also must he considered as the inhabi tants of the fresh water, which, in alternation with that of the sea, once occupied this spot. As the specimens des cribed by Faujas de St. Fond were also found in soils where vegetable remains were present, these also must be considered as of the same habits when living.