176 [September, 



generally overhung by the upper jaw, and sometimes both jaws are equal. The 

 pharyngeal teeth are of the grinding type and cultriform kind {Denies cullri/urjnes), 

 disposed upon a single series, with one exception only, and that occurs occa- 

 sionally in Campostoma. I say occasionallij , because in the majority of cases there 

 is also but one single row in the latter. Exoglossum is removed from this group, 

 of which it has none of the characters, except the absence of barbels. 



We introduce the tribe by the genus 



Campostoma, Agass., 



which may be characterised as follows : Head subconical ; body subfusiform ; 

 both compressed. Snout obtuse and protractile ; mouth inferior, though its 

 cleft is horizontal; lips very conspicuously developed; no barbels or cirrhi. Eyes 

 of moderate development. Isthmus very wide. Origin of ventrals situated in 

 advance of the anterior margin of the dorsal. Caudal furcated. Scales longer 

 than high. Pharyngeal bones strongly curved, with a small dilatation upon 

 their convexity. Teeth of the cultriform kind, of the grinding type, occasion- 

 ally slightly hooked. They are disposed upon a double row of four and one, in 

 the following manner: 44, or 1 | 4 4 | 1. 



1. Campostoma anomalum, Agass. Amer. Journ. of Sc. 2d ser. xix. 1855, 219. 

 Rutilus anomalus, Rafin. Ichth, Ohiens. 1820, 52. 



2. Campostoma ornatum is larger, more elongated and more fusiform than 

 C. anomalum. The^ead enters four times and a half in the total length. The 

 diameter of the eye enters nearly six times in the length of the side of the head. 

 The scales are much smaller than in C. anomalum. 



D 8-1-2 ; A 8 + 2 ; C 7, 1, 9, 8, 1, 6 ; V 8 ; P IG. 



The upper regions are purplish black ; the inferior regions golden brown and 

 yellow, with black spots distributed over the flanks. A black patch at the base 

 of all the fins, otherwise the latter are orange or yellowish brown. 



From Chihuahua River and a tributary only a few miles long. Collected by 

 John Potts, Esq. 



3. Campostoma FORMosnLUM. This species resembles more C. anomalum than 

 C. ornatum ; the most conspicuous difference between it and the former consist 

 in the presence of larger scales. The ground color is alike, but in C.formosulum 

 black irregular spots are distributed all over the upper region of the body. 



Numerous specimens collected in the Rio Sabinal, a tributary of the Rio San 

 Antonio, Texas, by Dr. C. B. Kennerly, under "W. 11. Emory, Commissioner U. S. 

 and Mexican Boundary. 



4. Campostoma nasutum. It is a shorter and more compact species, with the 

 peduncle of the tail rather tapering. Its most prominent character consists in 

 its thick and protruding snout, which overlaps the lower jaw more than in the 

 species already referred to. The ground color is greyish above, and whitish or 

 yellowish beneath ; upper region of body and flanks occasionally marmorated. 

 A black patch at the base of the caudal and dorsal fins. 



Specimens were collected by Lieut. D. N. Couch, U. S. A., at Cadereita, and 

 near Monterey, New Leon, in April, 1853. 



From the foregoing species of moderate size, we pass to a genus composed of 

 quite small fishes, differing from the former by the position of the ventral fins, 

 which are inserted either immediately under the anterior margin of the dorsal 

 fin or posteriorly to it, never in advance, as in Camjiostoma. To designate these 

 we have selected the name of 



DIONDA. 



They are very intimately related to the Hyborhynchi, and differing from them 

 by a smaller and more pointed head, a smaller mouth, though constructed upon 

 the same plan as in Hyborynchus, that is, the lower jaw being thin, flat and 

 rounded upon its periphery. The body is more slender and elongated, the snout 



