FISHES—CYPRINIDAE—DIONDA EPISCOPA. 
227 
This group has to include a much greater number of genera and species than was formerly 
anticipated. But, as a group, it must be based upon characters very different from those derived 
from the structure of the mouth. Indeed, those cartilaginous maxillar sheaths so prominent 
in Ghondrostoma, Cliondrocliylus, Chondrorhynclius and Lavinia, gradually become less and less 
conspicuous, until we find but a thin pelicle, such as occurs in other groups of the same family. 
DIONDA, Girard. 
Gen. Char. —Head sub-conical or sub-pyramidal. Mouth small, its gape somewhat arched; snout overlaping the lower jaw. 
Angle of the mouth not extending as far as the orbit. The eyes are large, moderate sized, or small. The isthmus is rather 
wide. Insertion of ventrals situated under the anterior margin of the dorsal or posterior to it. Caudal furcated. Pharyngeal 
bones stout, lower limb or branch as long as the upper. The teeth are of the cultriform kind, of the grinding type, compressed, 
not hooked; four are observed upon a single row, thus: 4—4. 
Syn. — Dionda, Grd. in Proc. Acad. Nat. Sc. Philad. VIII, 1856,176. 
Resembles Hyborhynclius , from which it differs by a smaller and more pointed head, a smaller 
mouth, though constructed upon the same plan as in Hyborhynclius, that is, the lower jaw being 
thin, flat and rounded upon its periphery. The body is more slender and elongated, the snout 
more protruding. The scales are either large, or else of moderate size, and the lateral line 
follows more or less the middle of the flanks. The dorsal fin is higher than long, and shorter 
than in Hyborhynclius , and the anterior ray is more closely united to the next. The insertion 
of the ventrals is always situated posteriorly to the anterior margin of the dorsal, or under it, 
never in advance of it. The pharyngeal bones are stouter than in Hyborhynclius, the lower 
branch or limb has the same length as the upper ; both are more curved, thus rendering the 
convexity of that bone more conspicuous; it is expanded as usual. The teeth are similar to 
those of Hyborliynchus, being, however, not quite so compressed and not hooked. 
This genus is closely allied to Campostoma, and since our Diondae are, generally speaking, 
small fishes, we should not be surprised at hearing that some of the species of Campostoma, 
while yet immature, could not always be easily distinguished from them, for, the mouth is, 
properly speaking, not smaller than in Campostoma. 
As to the genus Campostoma itself, it is treated of in the £ ‘Ichthyology to the United States 
and Mexican Boundary Survey,” where three species are figured and described. Several species 
of Dionda are likewise illustrated in the same report. 
1. DIONDA EPISCOPA, Grd. 
Spec. Char. —Body slender and sub-fusiform. Head sub-conical, blunt anteriorly, constituting the fifth of the total length. 
Eye large and sub-circular. Gape of mouth slightly arched, its angle not extending as far as a vertical line drawn in advance 
of the orbit. Caudal fin entering five and a half times in the total length. Insertion of ventrals situated somewhat posteriorly 
to the anterior margin of the dorsal. Scales large deeper than long. Blackish brown above, yellowish white beneath, spread 
all over with dark dots; a blaek streak from the snout across the orbit to the base of the caudal, where a black spot is likewise 
observed. 
Syn. — Dionda episcopa Grd., in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 177. 
The body is slender and graceful, sub-fusiform in profile, compressed, with the back slightly 
arched. The largest specimens observed measuring about three inches and a quarter. The 
head is large, forming about the fifth of the total length. The eye is large and sub-circular ; 
its diameter being contained three times and a half in the length of the side of the head: once 
