72 L. Agassiz on the Ichthyological Fauna of Western America. 
The family of Cyprinoids presents peculiar difficulties when- 
ever 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 repre- 
sentatives, 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 Neuchatel, 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 f intend to fill here in connec- 
tion with a more full description ‘of the species collected in Oregon 
and California by the naturalists of the expedition of Capt. Wilkes. 
e propriety of establishing new genera among Cyprinide 
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 con- 
tinent. 
Few Cyprinide have as yet been described from the fresh 
waters of the northwest coast of America, and the species brought 
home by the Exploring Expedition form an interesting addition 
to our knowledge 
The first question which arises a examining these fishes is 
North America, or do they resemble those of western Europe, or 
are they in any way related to the Asiatic types? As soon as 
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 tha t, with one exception, they 
correspond as little to any of the types ‘which occur in the eastern 
oa of the North American continent. They constitute in fact 
a benoit group of species, remarkable for the de- 
~lopalar ot their lips, and the horny aseraien which protects 
