reference to the identification of fossil remains. It is therefore plain that comparative anatomy should be more extensively and intimately combined with zoology than is generally the case. The classification of the animal kingdom should no longer be based simply upon the structure of the animals, but form and structure should everywhere and always be considered in their intimate connections.

I have already alluded to the narrow circumscription of the genus Lepidosteus, within the limits of the temperate zone of North America. In like manner, also, the Marsupialia, for instance, are almost wholly confined to New Holland, and the Edentata to Brazil. All this goes to show that there is an important connection between a given country and its inhabitants, which rests with the primitive plan of the creation.

The limited existence of Lepidosteus in North America in the present creation has, no doubt, reference to the fact that North America was an extensive continent long before other parts of the globe had nndergone their most extensive physical changes. Or in other words, that the present character of this continent has not been much altered from what it was when the ancient representatives of Lepidosteus lived; while in other parts of the world, the physical changes have been so extensive as to exclude such forms from among the animals suited for them.

We have therefore here a hint towards a more natural and deeper understanding of the laws regulating the geographical distribution of animals in general.

There are animals and plants whose detailed history is, as it were, at the same time, the history of that branch of science to which they belong. This is particularly the case with those animals, which, from particular circumstances, have thrown unusual light upon the relations which exist between them and their allied types. There are even a few such animals, the study of which has actually marked the advance of science. I cannot notice on this occasion the garpike without being strongly reminded how strikingly this has been the fact with Lepidosteus. The first sight I had of a stuffed skin of that fish in the Museum of Carlsruhe, when a medical student in the University of Heidelberg, in 1826, convinced me that this genus stood alone in the class of fishes; and that we could not, by any possibility,

associate it with any of the types of living fishes, nor succeed in finding, among living types, any one to associate fairly with it. It was a fact, at once deeply impressed upon my mind, that it stands isolated among all living beings; and this early impression has gradually led me to the views respecting classification which I have expressed above, and which have frequently guided me in appreciating both the various degrees of relationship, and also the differences which I have noticed among different families; and, I may say, has also kept me free from fanciful attempts at symmetrical classifications.

Somewhat later, my investigations of the fossil fishes led me to the distinct appreciation of the great difference there is between the characters of the class of fishes in early geological ages; I also noticed that all the bony fishes of former ages are more or less allied to the gar-pike, and widely different from the types of fishes now prevailing. But the real nature of this difference was only gradually understood. I had not yet perceived that the fishes of older times had peculiar characters of their own, not to be found either among the more recent fossils or among the living representatives of that class. But the opportunity of study ing the skeleton of Lepidosteus, which was afforded me in Paris by Cuvier, showed at once, that these fishes have reptilian characters.*

The articulation of their vertebræ differs from that of the verte bræ of all other fishes no less than the structure of their scales. Their extremities, especially the pectoral limbs, assume a higher development than in fishes generally. Their jaws also, and the structure of their teeth, are equally peculiar. Hence, it is plain that, before the class of reptiles was introduced upon our globe, the fishes, being then the only representatives of the type of vertebrata, were invested with the characters of a higher order, embodying, as it were, a prospective view of a higher development in another class, which was introduced as a distinct type only at a later period; and from that time the reptilian character, which had been so prominent in the oldest fishes, was gradually reduced, till, in more recent periods, and in the present creation, the fishes lost in

For further details, see my Recherches sur les Poissons Fossiles, Vol. II. part 2, p. 1-73.

the successive creations all this herpetological relationship, and were, at last, endowed with characters which contrast as much, when compared with those of reptiles, as they agreed closely in the beginning. Lepidosteus alone reminds us, in our time, of these old-fashioned characters of the class of fishes, as it was in former days.

An opportunity afforded me by John Edward Gray, Esq., of the British Museum, of examining a specimen of this genus, preserved in alcohol, furnished another evidence that the reptilian character of Lepidosteus was not only shown in its solid parts, but was even exemplified in the peculiar structure of its respiratory apparatus and its cellular air bladder, as I have pointed out in the Proceedings of the Zoological Society of London.*

One step further was made during this excursion, when, at Niagara, a living specimen of Lepidosteus was caught for me, and to my great delight, as well as to my utter astonishment, I saw this fish moving its head upon the neck freely, right and left and upwards, as a Saurian, and as no other fish in creation does.

This reptilian character of the older fishes is not the only striking character which distinguishes them. Investigations into the embryonic growth of recent fishes have led me to the discovery that the changes which they undergo agree, in many respects, in a very remarkable manner, with the differences which we notice between the fossils of different ages; so much so, that the peculiar form of the vertebral column, and especially its odd termination in very young embryos, where the upper lobe of the caudal fin is prolonged beyond the lower lobe, and forms an unequal, unsymmetrical appendage upwards and backwards, agrees precisely with the form of the tail of the bony fishes of the oldest geological deposits, so that these ancient fishes may be said to have embryonic peculiarities in addition to their reptilian character. This fact, so simple in itself, and apparently so natural, is of the utmost importance in the history of animal life. It has gradually led me to more extensive views, and to the conviction that embryonic investigations might throw as much light upon the successive development of the animal kingdom during the successive geological periods, as upon the physiological develop

* Proceed. Zool. Soc. of London, Vol. II. page 119.

ment of individual animals; and, indeed, I can now show, through all classes of the animal kingdom, that the oldest representatives of any family agree closely with the embryonic stages of the higher types of the living representatives of the same families; or, in other words, that the order of succession of animals, through all classes and families, agrees, in a most astonishing measure, with the degrees of development of young animals of the present age.

This being the case, it is obvious that a minute investigation of the embryology of Lepidosteus would throw a vast amount of light upon the history of the succession of fishes, of all geological periods; and also would probably give the first indication of the manner in which the separation of true ichthyological characters from reptilian characters, was gradually introduced; as it is more than probable, from all we know otherwise of the embryology of animals, that the young gar-pike, in its earliest condition, will have characters truly ichthyological, and only assume, gradually, the peculiar reptilian characters which distinguish it. But notwithstanding all my efforts to secure the Lepidosteus in the breeding season, I have failed up to this day to gain the desired information. It only remains for me, therefore, to urge naturalists living near the waters inhabited by Lepidosteus to take up the subject as early as an opportunity is afforded them.

Although Lepidosteus does not occur in Lake Superior, I have deemed it sufficiently important to introduce these remarks here, as this fish occurs in all the northern lakes except Lake Superior, as far north even as Mud Lake, below Sault St. Marie. Its presence in these waters is another of the striking differences which exist between the ichthyological fauna of Lake Superior, and that of the other lakes; and shows once more, within what narrow limits animals may be circumscribed, even when endowed with the most powerful means of locomotion, and left untrammeled by natural barriers.

This Lepidosteus is one of the swiftest fishes I know. He darts like an arrow through the waters, and the facility with which he overcomes rapids, even the rapids of the Niagara, shows that the falls of St. Mary would be no natural barrier to him, if there were no natural causes to keep him within the limits in which he is found, and which extend from Lake Michigan, Lake St. Clair, and Mud

Lake, through Lake Erie, and Ontario, down to the St. Lawrence and its outlet into the sea, into which this fish never ventures far, though he does not altogether avoid brackish and salt water.

Dr. Richardson was the first naturalist who described the northern Lepidosteus. He mentions it in his Fauna Boreali-Americana, under the name of Lepidosteus Huronensis, and gives a correct and detailed description of it. Nevertheless, it has been since mistaken, and referred to the southern species first described by Catesby and Linnæus, from which it is however very distinct, both by the proportions of its parts, its scales, its fins, and especially by the form of its frontal bones, in which the supra-orbital emargination is much lower and more elongated. Again, notwithstanding the descrip tion of Dr. Richardson, Dr. Dekay has redescribed it under the name of Lepidosteus Bison; and Zadock Thompson has described a young specimen under the name of Lepidosteus lineatus. At first, his description would seem to indicate a really distinct species; but I have ascertained, by a series of specimens, that the differences pointed out are really the characters of the young, and have no value as specific characters; the detached lobe formed by the upper raylets of the caudal fin is gradually united with the lower rays, and the longitudinal stripe, which is well marked in young specimens of a few inches in length, gradually vanishes, to leave only a few spots upon the sides, which even disappear entirely in the oldest individuals. The vertical fins alone remain spotted in the adult. The natural color of this fish is a light greenish gray, passing downwards into a dull white.

ACIPENSERIDE (Sturgeons.)

The family of Sturgeons is well characterized and easily distinguished from any other in the class. These fishes have generally been placed in the order of Chondropterygians, near the sharks, until I objected to this association, and attempted to show that, not

It is a very remarkable fact that several fishes of the old Red Sandstone period have, in their full-grown state, a peculiar form of their caudal fin, which is nearly identical with the form of the caudal fin of the young Lepidosteus; a form which is otherwise unknown to me at present in the whole class of fishes.