Of many hundred specimens dug from the guar-. ties of Bolca, the species amount to b• ; the rarity sir abundance of which • is extremely diversified, as well as the size of each. Some have been found 'three feet in length ; and, in 1789, the pegasus a small fish, was dug out of Lastrara, cchich, from its minuteness, almost escaped notice. Thus the natural agent affecting their transition from the ani mal to the fossil state, has equally operated on the bodies of all. A young shark, now preserved in a cabinet, merits particular observation. It is only 25 inches in length, wanting a small portion of the tail, and four in breadth • and more perfect than any of the same genus found in Bolca, though the remains of sharks of much larger size have been procured. The ravenous nature of the animal is disclosed by the contents of its stomach, which exhibits a quanti. ty of sea crabs • but it is wonderful to remark; that these are in a half digested stare. Considering the voracity of such fishes, it is evident that death must very soon have followed the capture of the prev. Certain appearances denote incipient putrefaction; which plainly proves, that the commencement. of the transition to the fossil state must have speedily ar rested its progress. . The sudden change which en sued is further corroborated by the skeletons of two fishes imprinted on the same stone ; one of which has seized the head of the other, and seems in the act of swallowing it. This is esteemed one of the most singular productions afforded by Bolca. The genus chmtodon has more frequently been described than others, either from readily occurring, or from being. better adapted for preservation. Scheuchzer long ago observed, that the chcetodon pinnatus, a fish commonly inhabiting the Arabian and Indian seas, was dug out of Boles ; and more•modern European' naturalists, on comparing the fossil with the real aril mal, ascertain, that, in the transition undergone, some parts have either enlarged or become defective. Thz chcetodon mesoleucus, lately transmitted from Japan, and which still lives in the seas of Africa also, is. found entire in Bolca. This fish, which is neither mentioned by Artedi nor Linnzus in its living state, was first discovered by. Forskhal on the shores of Arabia ; and Bloch afterwards received it from the island of Japan. Gmelin, however, in his edition of the •Systenza Naturce, probably being influenced by the remoteness of these two regions from each other, has formed two species, which seem to constitute• only one. The fossil extracted .from the .quar ries of Bolca corresponds with both. Among the finest specimens procured, is the durtodon argus, bearing a minute and perfect resemblance to that caught in the rivers of India, or in stagnant where it feeds on insects, and animal substances sup-. plied to it The cluctodon argus is conjectured to. pass through extensive seas, for it has been described as inhabiting places many degrees asunder. So far as hitherto. ascertained, the cluetodon arcuatus has never been seen in the European seas, yet it is dug out of Bolca. Marcgrave enumerates it among the fishes of Brazil, and Artedi classes it with those in. habiting India. Two specimens from the hill, which are still preserved, first proved it to have. anciently existed in Europe. There is a fish of uncommon structure, called the sea bat by the older ichthyolo_ gists, and thence cheetodon uespertilio by the mo-• Berns, which very few have described. Willoughby . speaks of .it, but. it was unknown to Linnaeus, and seems to be .found solely in the seas surrounding the island of Japan. One individual, of small size, has come uncle- the inspection of a celebrated na turalist ; but another, considerably larger, though in a fossil state, has been taken from the excavations of Bolca. The la ttt''' is ten inches in _length, from r = ..vtreme head to tail, and nineteen and a naic breadth : Several of the pectoral and ventral fins are defective, but their origin is still quite conspicuous. Two other specimens of the same fish are likewise ex: tant. A species of ray, which is scarce to be re cognised in the European seas, was found in the im mediate vicinity of Bolca, along with three univalve fossil shells imbedded in the same stone. It is twen ty-three inches long, and nine broad, and exactly resembles a new species inhabiting Arabia, called raja sephen • some are discovered three or four times as large. The fishes of Mount Bolca are by no means confined to genera and species now extant ; for various specimens have appeared hitherto undescri: bed, and which are still unknown. The uranoscopus rastrum, so named in its fossil state, has never been seen as a living animal ; and the most careful compa risons of all the specimens found, remove it from any analogous species. We shall dwell no longer on*his division of the natural products of Bolca ; catalogues of which have been published in Italy, shoving what species belong to the seas of the four quarters of the globe, and what are exotic fresh water fishes. Be. sides these, several rare species of fossil crabs are ob tained from the quarries such as the longimanus, se fifer, and locusta, of the specimens are parti Cularly fine. Among the insect tribes, there have been dug tip an onsscus, oestrus, two asili, and an American cimex. Complete exuvhe of marine ser pents are sometimes, though rarely, laid open ; and numbers of marine plants arc imprinted on the stones. The parts of birds are less frequent in a fossil state than those of any animals; but a petrified quill was once found in Bolca, and lately preserved at Verona, as an exception from the general rules of nature in accomplishing this extraordinary transition.
A profound and interesting problem arises on the formation of this singular hill, and the substances which it contains. First, How can such an aggre gate of animals, inhabiting regions so many geogra phical degrees asunder, have been collected in so li mited a space ? Secondly, How are the fishes inha biting salt and fresh waters respectively, which may' almost be denominated different elements, intermixed ? And, thirdly, How have the bodies of such soft and destructible animals been able to resist the usual de composition of nature, undergo a transition to stone, and remain entire from a period of such remote anti quity ? Various theories may be offered on these questions, which, in this place, we shall not pre tend to discuss, as they will partly come under our consideration in other articles. But there are some
points which peculiarly relate to Mount Bolca it self, on which we shall make a few observations.
It is evident that the sea has once overflowed the highest mountains. Beds of shells, and strata of cal careous substances, added to the impression of fishes on stone, besides many other concurring circumstances, prove the truth of this assertion. It is clear, there fore, that the Veronese territory, which presents all these indications in the most conspicuous manner, may have anciently been submerged, or even may have been the bottom of the sea. In various portions of the globe the waters have receded ; and we know, that, in certain places, their gradual retreat has been • - aaes. At the same slowly exnioiteu ' at time, it is not improbable that they may here 114*. once been withdrawn by some violent convulsion of the earth ; a fact which has been exemplified in the course of the preceding centuries. But supposing that they naturally covered the Veronese territory, it is far frOm easy to account for the diversity of fishes belonging to remote climates being found in the same spot, especially as the heat of the torrid zone seems indispensible to their existence. Yet, without recur ring to the gradual refrigeration of the earth, .or the gradual change of.climate in limited districts, which we are well assured has followed, two circumstances ought to be preserved in view : Nothing can be more imperfect than our acquaintance with the finny tribes. Genera and species innumerable have never met the eye of mankind ; and it is justly remarked by a mo. dern ichthyologist, that our principal knowledge of their distinguishing characters have first been derived from those served up at our repasts. Can we affirm with confidence, that any fish of the Mediterranean is unknown in the Pacific Ocean, or that many in the Greenland Seas do not frequent the shores of Bri tain ? Skilful naturalists are aware, that animals arc daily discovered in one region, that have been refer. red to and described as peculiar to another ; and that, with care and attention, even when removed from their original liberty, they may be preserved and propagated in climates not naturally their own. Nei. ther can we overlook an important fact, relative to the temperature of the elements, which terrestrial and aquatic animals respectively inhabit. The air is subject to constant vicissitudes from external causes, but it is probable that the temperature of a vast body of water always continues at nearly the same degree ; nay, it is probable, that, with the exception of ex• treme cases, the temperature of the sea, above fifty fathoms deep, is not very different all over the world. Hence it is possible, supposing the genera of Mount Bolca and those of the Indian Seas to be identified beyond dispute, that both may have enjoyed a requisite• degree of temperature when a deep sea covered the territory of Verona. Fishes, however, are more pri vileged than terrestrial animals, in the facilities of seeking a temperature agreeable to themielves ; if the' surface of their element undergoes refrigeration, have only to plunge farther into its depths ; and the body being too immense to be susceptible of suddem vicissitudes, they have time to withdraw from one parallel of latitude to another, as their sensations may require. We know, that certain fishes can support considerable change of climate without injury ; and• that some, transported north from places far to the southward, have been naturalized. Thus, we can not with absolute confidence maintain, that the hitherto thought peculiar to the warmer climates could not live in the seas covering Mount Bolca, or that they did not enjoy that degree of temperature %Aid' was necessary to their nature.- Perhaps those seas may have been heated by the effects of the volca noes, whose remains are scattered over the territory ; for although great bodies of water cannot be sud denly affected by a change of temperature, the shal lows immediately surrounding volcanic mountains and isles have been known to melt sels sail;-• ' or yes close by their sides. Such shallows are alivays a grateful abode to fishes : there they flock together in numbers, and perhaps find more copious supplies of food in the marine insects which the heat conspires to propagate and diffuse. The atmosphere likewise greatly heated by the fires of constant volcanoes ; and it has been affirmed, that one of the most productive islands in the globe is rendered so, principally by the constant flames of eight volca noes. In this way, the temperature of the Veronese territory may have anciently been augmented. It is infinitely more difficult to explain how salt and fresh water fishes are intermixed ; • for although it be very possible, that, by gradual and almost im perceptible transitions, they might be reciprocally brought to live in either ; or successive generations, by passing from greater or lesser degrees of saltness or freshnes while in the ovular state, might habituate the perfect animal to the change ; as we have not witnessed the fact, we cannot maintain that it has taken place. Still it is to be remembered, that some fishes dwell in salt or fresh water indiscriminately ; that we do not know whether confinement to one of them only is destructive ; and that there is a minute resemblance between the species of the same genera which inhabit both.