SYNBRANCHUS. Another from the same source. These three last are rather supposed to belong to the Cxcilia of Dumeril, which is a common fish in the Mediterranean.
This terminates the list of the fishes of Monte Bolca, and the whole subject demands a few remarks. We have given our opinion in a more proper place, respecting the geological nature of this piece of ground, and the causes owing to which it contains so many fishes, and in that par ticular state in which they are found. If our views be correct, they should all he marine fish ; and the greater number, at least, should belong to the present surrounding seas. We cannot be sure respecting the whole, because it is quite possible that genera and species of fish may be destroyed in the progress of time, as so many land animals have been. But if the deficiencies of analogy in the fishes of Monte Bolca to those of the present Mediterranean are too considerable to admit of this solution of the difficulty, the cause may consist partly in our not having yet seen all the living individuals of that sea ; and, as must be fully obvious from the preceding remarks, far more in the ex treme imperfection of many of the fossil specimens, and in the impossibility of coming to any decision respecting these.
But to examine this a little more particularly. Volta enumerates 105 species; while M. Blainville, who is as suredly not wanting in good will towards the formation of new species and genera out of imperfect fragments, with difficulty allows of 92. Volta decides also, that seven spe cies are fresh-water fish ; while Blainville does not admit that there is one that is not marine ; a conclusion in which, on geological evidence, we must agree with him. Fur ther, it is Volta's opinon that out of the remainder, twen ty-seven are European species, and thirty-nine Asiatic ; that three belong to the African coast, eighteen to South America, and eleven to North America. M. Blainville very properly doubts of this on ichthyological grounds; and on geological ones we have no hesitatation in saying that it is impossible. In fact, if we examine those details of the fossil specimens, which we could not have given without far transgressing our limits, we shall find that, wherever a specimen is tolerably perfect, there is little or no difficulty in referring it to an existing species ; and of those that are fragments, it is perfectly futile to attempt to assign their names, and far worse than futile to look for their analogies in distant seas. We have little doubt that
the species of this spot might be reduced to a still smaller number, and that probably almost every one of them is now a Mediterranean fish.
Ichthyolites, but in comparatively small numbers, are found in other parts of Italy, and among the most remark able are those of the Vicentine.
At Shio, according to Faujas, they are found in com pressed spheroidal nodules inclosed in calcareous beds, the geological characters of which are not described. Only one species of chwtodon has, however, been disco vered here, about nine inches long and seven in breadth.
At Monteviale, according to the same author, the spe cimens are found in a brown, bituminous, argillo-calca reous shale, and they consist also of a small species of cha todon. Specimens of a similar nature occur at Salzeo, twenty miles to the northward of Vicenza, at the foot of the Tyrolese Alps, in a black, fissile, pyritical schist, on the summit of a volcanic mountain. Ichthyolites occur also at Tolmezzo, but the species are not described. At Murazzo Struzziano, a specimen has been found, which is considered as a Clupea, and called Dentex.
Dalmatia produces some specimens of fossil fish, but they continue undescrihed, as do those of Cerigo. Those of Mount Lebanon are supposed to bear a resemblance to the ichthyolites of Pappenheim ; being mere skeletons, but generally pretty entire, flattened by pressure, and with some traces of scales. The rock is a schistose, fetid, argil laceous limestone. Two species have been supposed ca pable of being referred to the genus Clupea, and they are called Brevissima and Beurardi. One, somewhat similar to the last, has also been found at Acre.