FISHES FROM CENTRAL AND NORTHERN MEXICO. 
5T 
RIO DE LOS CONCHOS AT CHIHUAHUA, MEXICO. 
The river bed of the Eio de los Conchos, at Cdiihuahua, is more than half a mile in 
width, witii numerous sand bars and depressions. It is, however, very little more than 
abed, owing to the almost total lack of rainfall in this region throug’hout the year. 
Hence, the water in this large river bed is reeluced to a very diminutive stream, which 
is brought from the mountains, 10 miles distant, by an aqueduct, to supply the city. 
About a lidle below the city the stream is dammeel, in order to make the water avail- 
able for irrigation. Here on one side tlie bank is high and rocky, and the water 
entirely too deep for seining. The other shore is composed of a sand bank that slopes 
very gradually to the deeper water, and is easily accessible. The bed of the river is 
covered with several inches of mud; and, in the more shallow places, is thickly over- 
grown with waterweeds and other vegetation. Tlie more quiet waters swarm with 
small Ashes, which, for the most part, belong to the family Cyprinidcv. At the upxier 
end of the pond, caused from damming tlie waters, is a clear, shallow'' rixixile, from wdiich 
a number of darters and two or three species of GyprinodonUdce were taken. The fol- 
lowing siiecies were collected from this stream: 
1. Campostoma oniatum Girard. This Avas one of the most abundant spfecies in this locality. The 
adults differ but little in color and general shape from Campostoma anomahnn ; the sides, and 
especially the caudal pediincle, were marked with scattered dark siiots; dark humeral bar 
present; orbit small and rounded. Head in length, 4; depth in length, 4-}-; eye in head,, 
5-[-. Four specimens of an aA^erage size measured as follows: 
Leiigtli. 
Head. 
j Deiitli. 
Eye. 
Lateral 
line. 
mm. 
mm. 
j mm. 
mm. 
85 
22-5 
\ 21 + 
4 
73 
so 
20 
20 
4— 
73 
77 
20 
1 18 
4 — 
72 
77 
20 
1 
1 
4— 
72 
2. Pimepliales promelas confertus (Girard). Tavo specimens taken ; one a very large male with 
A^ery bright colors, black AAnth two broad light crossbands; pectoral fins white, excepit the 
black outer edge, Avhich is followed by a narrow, sharply defined streak of sih-er. Lateral 
line complete. 
3. Couesitis adustus sp. nov. Body moderately eleAmtcd, compressed; the back a little elevated, 
the anterior profile someAvhat coiiA'ex; snout rather long, slightly pointed, 3J- in head; 
mouth loAv, terminal oblique, the jaAvs subequal, the maxillary opxrosite the i)Osterior nostril ; 
barbel small, liattish; eye moderate, 3f to 4 in head; preorbital broad; interorbital space 
Ijroad; scales small; those before dorsal and on belly smaller; lateral line decuiwed. Dorsal 
inserted a little behind A'entrals, high and p)ointed ; lower fins short, the pectorals not reaching 
A'entrals, the latter to vent. OliA'aceous, dusky aboA'e, sides sih-ery; a narrow plumbeous 
lateral band ending in the young in a small black caudal spot, obsolete in the adult ; fins all 
plain. Head, 41; depth, 4|; D. 8; A. 7. Scales, 13-58-8, 27 before dorsal; teeth, 2, 4-4, 2. 
Length, 102 mm. Three siiecimens were taken in the Eio de los Conchos at Chihuahua. 
The smallest, 65 mm. long, is more sih-ery and Avith the back somewhat arched; the barbel 
Ijroportionally much longer and the black caudal spot distinct. It is probably, hoAA-eA-er, 
of the same species as the others. 
4. Leuciscus nigrescens (Girard). {Tir/omank/vescens, Tigoma puJchra, and TUjoma pul chcUa Girard, 
Proc. Acad. Nat. Sci. Phila., a'iii, 1856, 207; Clinostomus pandora and Glia guJa Cope.) 
Body elongate; head long, conical; month large, terminal, slightly oblique; back, 
slightly arched, shoulders heavy; dorsal Avell behind A'entral ; anterior part of dorsal mid- 
