einen, “ol 
4 
4 
6 
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L. Agassiz on the Ichthyological Fauna of Western America. 229 
pity that neither pharyngeal bone nor intestines have been pre- 
served so that the relation of this fish to the ordinary Leucisci 
cannot be well ascertained. 
I have preserved the characteristic of this genus as I had writ- 
ten it four years ago when I had only the specimens of the Ex- 
ploring Expedition before me, without any trace of pharyngeals 
or intestines, that I may be able better to show how correctly we 
may judge of certain structural peculiarities not within our reach 
from other facts we may have observed. The 17. 
predatory habits of the type of this genus were 
inferred from the form of its body and from the 
shape of its mouth. Now we know also the 
teeth from another species sent me from San 
Francisco by my friend 'I'. G. Cary, Jr., Esq., 
the case is perfectly plain and 1 am confident 
in asserting that the species of Ptychocheilus | 
areamong the most voracious of the whole 
family of Cyprinoids, exceeding probablyjall 
others in their rapacious dispositions. 
Fig. 17, a, represents the right pharyngeal 
of Ptychocheilus major, from behind; 8, one ° 
of the teeth of the outer row magnified twice. 24 
Ptychocheilus gracilis, Agass. & Pick. 
The back bluish grey. Silvery upon the sides. Head and 
cheeks golden color. Fins yellowish orange. The middle of the 
caudal grey. 
From Willamet Falls, Oregon. 
Ptychochetlus major, Agass. 
_Tam unable to indicate the colors of this species, but it is easily 
distinguished from the preceding by its larger scales. 
rom San Francisco, California. 
Mylocheilus, Agass. 
It seems to be a characteristic feature of the Cyprinide of the 
Columbia River, to have their mouth clothed with a hard grind- 
ing sheath similar to the horny covering of the Turtles. e 
have seen the Acrocheilus provided with a flat horny chevron upon 
its lower jaw, and a similar but narrower sheath upon the inner 
margin of the upper lip. In the genus Mylocheilus the mouth has 
a different shape. At first sight it does not differ at all from that 
of the common Leucisci, or rather from the type which repre- 
Sents the European Leucisci on the shores of North America, and 
of Which Dr. Storer’s Leuciseus pulchellus is this type, which 
differs from the European Leuciscus in having a small tentacle, 
: European Gudgeon upon the angle of the upper jaw be- 
