FISHES—CYPRINIDAE—MYLOCHEILUS CAUEINUS. 
213 
we are able now to offer to our readers. Although years have already been devoted to this 
report, the subject is one of such magnitude that justice could not be done to it in all its parts. 
But as already stated, such families as are now briefly passed in review will be taken up seriatim 
hereafter. A good deal is to be added to the Iconography of this family, and many corrections 
are demanded upon several of the accompanying figures. 
TRIBE OF CYPRXItf/. 
Of the two genera of this group or tribe, whichever called, that have come to our knowledge 
within the territory, the ichthyic fauna of which we have now under investigation, one is 
provided with a buccal or rather maxillar barbel {Mylocheilus) , whilst the other has none 
{Mylopliarodon). The presence or absence of barbels, therefore, does not seem of primary im¬ 
port here. The teeth are of the molar kind (Dentes molares) of the grinding type (JD. masti- 
catorii ), without grooves or ridges, and are disposed upon two permanent—and a third, 
deciduous—rows, thus: 3 | 2 | 5—5 | 2 | 3. The ventrals are inserted in advance of the ante¬ 
rior margin of the dorsal. 
Syn. — Oyprini, Grd. in Proc. Acad. Nat. Sc. Philad. V [II, 1856, 168. 
MYLOCHEILUS, Agass. 
Gen. Char. —Head elongated and sub-conical, rounded upon the snout, which overlaps the lower jaw. The mouth is sub¬ 
terminal, horizontal, of medium size, and provided at its angle with a maxillar barbel. The eye is well developed ; the isthmus 
rather narrow. The body is elongated, lanceolated, compressed, sub-fusiform in profile. Pectoral fins slenderer than the vcn- 
traJs, the latter being inserted under the anterior portion of the dorsal. Caudal fin furcated. Scales of medium size, longer 
' than deep, with radiating grooves upon their posterior section only. The lateral line follows the middle of the flanks. The 
pharyngeal bones are stoutish, expanded upon their convexity, with the inferior limbs very short. The teeth are inserted upon 
a very much inclined plan, raised from the surface of the bone itself, from below upwards. They are disposed upon two per¬ 
manent rows of five and two, and a third deciduous row of three in the thickness of the gum : 3 | 2 | 5—5 | 2 | 3. They are 
of the molar kind of the grinding type, but without grooves and ridges. 
Syn — Mylocheilus, Agass. in Amer. Journ. of Sc. 2d series, XIX, 1855, 229.— Grd. in Proc. Acad. Nat. Sc. Philad. 
VIII, 1856, 169. 
We are acquainted so far with but two genera of this tribe within the limits of the United 
States, both being peculiar to the western slope of the Rocky mountains. 
1. MYLOCHEILUS CAUEINUS, Grd. 
Plate XLYI, Figs. 1—4. 
Spec. Char. —Head entering four times and three quarters in the total length. Snout rounded and sub-conical, though 
rather blunt. Posterior extremity of maxillary extending to a vertical line drawn across the posterior rim of the hind nostril. 
Diameter of the eye contained five times and a half in the length of the side of the head. Anterior margin of dorsal fin nearer 
the insertion of the caudal than the extremity of the snout. Anterior basal edge of ventrals situated opposite the third developed 
ray of the dorsal. Base of anal fin contained twelve times in the total length. Brownish black - above ; yellowish gold beneath. 
Two lateral darker bands, the inferior one not extending quite so far back as the vent. 
Syn. —Cyprinus (Leuciscus) caurinus, Rich. Faun. Bor. Amer. Ill, 1836,304. 
Mylocheilus caurinus, Grd. in Proc Acad. Nat. Sc. Philad. VIII, 1856, 169. 
This species bas much of the general appearance of the following two, more, perhaps, of M. 
fraterculus than M. lateralis. The most prominent difference resides in the pharyngeal bones 
being less expanded upon the superior limb, which is much more developed also. The inferior 
