posed that the rise and fall which takes place during periods of from three to seven years, to be possibly the effect of increased depth of water in the Lake, caused by an unusual amount of snow on its borders and tributary streams, or an uncommon rainy season; and that it even appeared from au extract from the New York Advertiser, that a gentleman just then (1828) returned from a tour to the West, had informed the editor that the waters of Lakes Ontario and Erie were then nearly a foot higher, while those of Lake Superior were considerably lower than ever known. The General was therefore led to suggest that, to obtain full, and exact data as to the rise and fall of the different Lakes tideguages should be placed at a number of points on the shore of each, both in their narrowest and broadest dimensions, and the changes carefully observed for a whole year, or at least for several months, and accurate tables kept of the times and extent of each flux and reflux, in which the position, as respects the meridian. and the phases of the moon, and also the course of the winds should be noted;-a plan which, it will be perceived, is very similar to that proposed by myself in my late paper on the establishment of simultaneous meteorological observations.

(To be continued.)

ART. XII.-Synopsis of the Ichthyological Fauna of the Parific slope of North America, chiefly from the collections made by the U.S. Expl. Exped. under the command of Capt. C. Wilkes, with recent Additions and Comparisons with Eastern types; by L. AGASSIZ.

CYPRINOIDS.

In order rightly to appreciate the natural relations of the representatives of this family living in the fresh waters of the western slope of this continent, to those found in the waters of its eastern slope and elsewhere, it is important first to reconsider the many genera established by Rafinesque in his "Ichthyologia Ohiensis," as well as those recently added by Messrs. Baird and Girard, and to institute a careful comparison between them and those founded by European ichthyologists; for though it is gratifying to behold the zeal with which important additions are daily making to our fauna by the activity of the scientific members of the various expeditions which have lately explored the western parts of the United States by order of the Central Government, it is deeply to be regretted that no more criticism is displayed in the notices which have been published descriptive of these animals. Instead of careful comparisons with more or less allied foreign forms, we are presented with such descriptions of our fishes and reptiles, as would leave the impression that nothing like them is to be found in any other part of the world,

The family of Cyprinoids presents peculiar difficulties whenever we attempt to characterise its genera, as is too well shown by the conflicting views of those who have written upon this subject.

This difficulty arises chiefly from the uniformity of its representatives, greater than is observed, in most other families, and also from the necessity of resorting to dissections to trace their most important characteristics.

In a paper published in 1834 in the Mémoires de la Société des Sciences Naturelles de Neuchâtel, I have however shown that reliable characters may be obtained from the pharyngeal teeth, and the more recent investigations of Heckel upon this subject have confirmed my statements and extended them over a large number of genera and species unknown to science at the time I published the results of my first investigations. At the time Heckel published his valuable remarks upon Cyprinoids, he seems to have been but scantily provided with American representatives of this family.

It is this gap in our knowledge I intend to fill here in connection with a more full description of the species collected in Oregon and California by the naturalists of the expedition of Capt. Wilkes.

The propriety of establishing new genera among Cyprinidæ will appear very questionable to the ichthyologists who have traced the almost endless divisions to which this family has of late been submitted. Nevertheless I feel compelled to introduce some new divisions among them, to classify several fishes which have been collected by the United States Exploring Expedition, and some others long known from the eastern parts of this continent.

Few Cyprinidæ have as yet been described from the fresh waters of the north west coast of America, and the species brought home by the Exploring Expedition form an interesting addition to our knowledge.

The first question which arises upon examining these fishes is naturally,—to what genus do they belong? Are they in any way analogous to the Cyprinidæ of the eastern or Atlantic side of North America, or do they resemble those of western Europe, or are they in any way related to the Asiatic types? As soon as I knew that species of that family had been preserved among the collections of the Exploring Expedition, my first care was to examine their generic relations, and, to my utter astonishment I found that they do not belong to any of the numerous genera established by myself, Heckel, Prince Canino, or McLelland for the species of the old world, and that, with one exception, they correspond as little to any of the types which occur in the eastern parts of the North American continent. They constitute in fact by themselves a natural group of species, remarkable for the development of their lips, and the horny covering which protects

the outline of the month. Their pharyngeal teeth also, as far as I have been able to ascertain, have a peculiar structure. Even if the subdivision of the Cyprinidæ into genera had never been extended beyond the limits marked out by Cuvier, three, at least of the species from Oregon should be admitted as new types of this family, for which genera I shall propose the names of Mylocheilus, Ptychocheilus and Acrocheilus.

TRIBE OF CATOSTOMI.

Heckel subdivides the family of Cyprinoids into ten tribes, the fourth of which embraces our Catostomi. This tribe is very natural, if we exclude from it the genus Exoglossum, the true affinities of which are with Chondrostoma and not with Catostomi as Heckel admits. The true Catostomi have very remarkable pharyngeal bones, with a large number of compressed teeth, arranged like the teeth of a comb, upon the inner prominent edge of these bones, and gradually increasing in size from above downwards, whilst in Exoglossum the teeth are few in number, obliquely truncate and occupying only the middle of the curve of the pharyngeals as in Chondrostoma.

For a long time past I have songht in vain to find out the homology of these curious pharyngeal teeth, so peculiar, and so characteristic in the family of the Cyprinoids. It was not until I began to investigate the various types of the old genus Catostomus, that I found a clue to their true significance. The armature upon the inner curve of the branchial arches of Cyprinoids differs so completely from the common type of their pharyngeal teeth, in the genera of the old world, that even a comparison between them is hardly suggested; but in Catostomus the extensive row of comb-like teeth, upon the posterior edge of the inner margin of the pharyngeal arches is so combined with a row of horny serratures upon the anterior edge of the same margin, that the homology of the two becomes at once obvious. See fig. 2, a' and a". The pharyngeal teeth correspond to the armature upou the inner curve of the branchial arches; they may, however, be either simple epidermic serratures or papillæ, or assume the structure of genuine teeth and become soldered to the bone upon which they are formed, as is the case also with the maxillary teeth of so many fishes.

Notwithstanding the similarity of the general arrangement of the pharyngeal teeth in all Catostomi, there are still such differences in their form and number, and especially in the shape of their inner edge, that these peculiarities afford additional evidence. of the propriety of acknowledging several genera among them, most of which have already been indicated, though very indifferSECOND SERIES, Vol. XIX, No. 55.--Jan., 1855.

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ently characterised by Rafinesque. In order to ascertain beyond a question the generic value of these characters I have examined the pharyngeals of every one of the species described in this paper, and of several of them compared a number of specimens of different ages and sexes with one another, and I have invariably found that within the limits within which the genera are circumscribed here, they present a peculiar type for each genus, reproduced in the different species with slight variations in the size and proportions of the teeth, the strength of the arch and the length of its symphysis.

Thus far the whole tribe of Catostomi must be considered as belonging exclusively to North America, the true relations of the Catostomus Tilesii, founded by Valenciennes, upon the description of the Cyprinus rostratus, from Northern Asia, by Tilesins being still doubtful, or wanting at least the only confirmation acceptable in our days, that is based upon a direct comparison of original specimens. Catostomi are found as far south as Texas and along the northern boundaries of Mexico, as is shown by the descriptions of several species published by Messrs. Baird and Girard in the Proceedings of the Academy of Natural Sciences of Philadelphia for 1854, but I have been unable to ascertain whether they inhabit the waters of Cuba.

It is a very interesting fact that while America has no native representation of the tribe of Carps, some of its Catostomi, the Carpiodes, Ichthyobus and Bubalichthys, remind us strongly by their external appearance of the true Cyprini of the old world, whilst others, the Cycleptus and Moxostoma resemble more the Borbus of Europe, Asia and Africa and the Tinca of Europe, which are also entirely wanting in America, and still others, the Catostomi proper have not even analogous representatives in the eastern continents.

Carpiodes, Raf.

1. The body is very high and strongly compressed, the narrow ridge of the back forming the outline in front of the dorsal is very much arched, and regularly continuous downwards with the rather steep profile of the head.

The head is short, its height and length differ but little. The snout is short and blunt. The small month is entirely inferior, and surrounded by narrow thin lips, which are more or less transversely folded. The lower jaw is short and broad.

The pharyngeal bones of Carpiodes are remarkably thin, compressed laterally, with a shallow furrow along the anterior margin on the inside, and another more central one on the outline of the arched surfaces; the teeth are very small, compressed, equally thin along the whole inner edge of the bone, forming a fine comblike crest of minute serratures; their cutting edge rises above the

inner margin into a prominent point. Fig. 1, a, represents the inner surface of the right pharyngeal, b, the dental edge of the two pharyngeals in their natural position, c and d, magnified teeth in profile.

1.

b

The anterior lobe of the long dorsal is slender, its third and fourth rays being prolonged beyond the following ones into long filaments. The lower fins are all pointed, rather small, and hence distant from one another. The ventral ridge of the body is flat. The scales have many narrow, radiating furrows upon the anterior field, and one, more deeply marked, in a straight line, across the lateral fields, or limiting the lateral and posterior fields, hardly any upon the anterior field, the waving of the broader concentric ridges producing only a radiated appearance upon that field. Tube of the lateral line straight and simple, arising in advance of the centre of radiation, which is seated in the centre of form of the scales.

Cuvier referred erroneously the type of this genus to his genus Labeo, in which he has been followed by DeKay, whilst Valenciennes founded upon it his genus Sclerognathus. Rafinesque however, had already called it Carpiodes; this latter name having the priority, must therefore be retained. Moreover Valenciennes describes as a second species of that genus under the name of Sclerognathus Cyprinella, a fish from Lake Pontchartrain, which belongs to Rafinesque's genus Ichthyobus, as I shall show below. In recognising the generic differences which distinguish these two fishes, Rafinesque has really been much in advance of more recent observers, though the characteristics he ascribes to them are very loosely and imperfectly drawn.

I know now four species of this curious genus, oue of which inhabits the fresh waters of our middle States, emptying into the Atlantic, the Catostomus Cyprinus of Lesueur; another occurs in Lake Champlain and the waters of our Northern States, emptying to the St. Lawrence, the Catostomus Cyprinus of the Rev. Zad. Thompson; a third is found in the Ohio, and its tributaries, and has been described under the same name as the preceding ones, by Dr. Kirtland in his "Fishes of the Ohio." I have lately obtained a fourth from the Osage River, through the kindness of Mr. George Stolley, which I have inscribed as Carpiodes Bison in my notice of the Fishes of the Tennessee River.* It occurs also in the Mississippi, above its junction with the Missouri, as I have ascertained recently from specimens forwarded to me by Dr. Rauch of Burlington, Iowa; whether it is found farther south, 1 do not know.

* See this Journal, 2nd Ser., vol. xvii, p. 356.