FISHES FROM THE RIVERS OF MEXICO. 
125 
from tip of snout to base of caudal; ventrals extending to vent; tips of pectorals reaching ventrals; 
caudal deeply forked. 
Color silvery; a narrow, dark median band extending from occiput to base of caudal; dorsal 
scales with fine dots which give their edges a dusky color. 
One specimen was taken, careful measurements of which are given. Length of body in milli- 
meters 71; depth of body expressed in hundredths of length 25; depth of caudal peduncle 11; length 
of head 25; width of interorbital space 7 ; length of snout 7 ; diameter of orbit 7 ; distance from snout 
to dorsal fin 47 ; height of longest dorsal rays 26; distance from snout to anal fin 67 ; height of longest 
anal rays 21; distance from anal to caudal fin 27 ; length of caudal fin 31|; length of pectoral fin 22; 
distance from snout to ventral fin 62; length of ventral fin 21. 
14. Hybopsiti altus (Jordan). 
Many specimens from the Rio Verde, Aguas Calientes, some of which were 165 millimeters long. 
CHARACINIDAl. 
15. Tetragonopterus mexicanus Filippi. 
Specimens of Tetragonopterus caught in the Rio Ixtla at Puente de Ixtla, Morelos, resemble very 
closely those taken in the Rio Verde near Rascon, but we believe that they belong to a different 
species. Besides the points of difference expressed in the following table, T. mexicamis of the Rio Ixtla 
has smaller and weaker teeth than T. argentatus of the Rio Verde. 
Average measurements of ten specimens each of Tetragonopterus mexicanus from the Bio Ixtla 
and of Tetragonopterus argentatus from the Bio Yerde near Bascon. 
Measurements. 
Tetragon- 
opterus 
mexicanus. 
Tetragon- 
opterus 
argentatus. 
Length of head expressed in hundredths of length 
25. 10 
28. 75 
Distance from snout to occiput 
25. 25 
28. 25 
Distance from lower jaw to occiput 
20. 50 
28. 80 
Width of interorbital space 
8.80 
9. 70 
G. GO 
7. 09 
8. 40 
10. 10 
Distance from snout to origin of dorsal fin 
51.25 
54. 30 
Measurements of ten specimens of Tetragonopterus mexicamis. 
Measurements. 
Locality: Kio Ixtla at Puente de Ixtla, 
Mexico. 
Morelos, 
48 
55 
59 
52 
35 
124 
51 
79 
34 
12 
79 
OO a 
CO CO I- 
94 
Depth of body expressed in hundredths of length. . . . 
35 
12 
34 
12 
38 
124 
36 
12 
35 
12 
38 
124 
26 
23* 
25* 
9 
' 39 
124 
25 
24 
25 
26“ 
'26" 
26 
26 
24 
244 
26" 
24 
24 
26 
25 
25 
2G 
264 
27“ 
27 
28 
26 
24 
27 
26 
27 
94 
9 
8 
9 
Si 
74 
9 
84 
0 
84 
9 2 
6 
6 
7 
7 
6 
7 1 
6| 
7 
9 
8| 
524 
8 2 
9 
9 
8 
S' 
8 
8 
8 
54 
524 
374 
50 
514 
37' 
26 
64 
50 
52 
52 
53 
50 
35 
364 
37 
38 
23 
374 
35 
36 
25 
25" 
26“ 
26 
21 
22" 
24 
23 
69 
68 
63 
66 
13 
67 
69 
67 
664 
15 
15 
164 
17 
16 
15 
13 
15 
14“ 
14 
15 
15 
15 
164 
15 
15 
16 
274 
33 
31 
30 
27" 
28 
28 
30 
28 
23 
2l” 
9.9.! 
24 
20 
20 
21 
52 
21 
49 
48 
50 
47” 
51 
484 
15 
49 
50 
1G 
16 
18 
18 
17 
16 
15 
17 
154- 
9“ 
23 
10 
10 
10 
10 
10 
9 
10 
23 
]0 
9 
09 
23 
21 
21 
23 
12 
21 
21 
20 
14 
14 
14 
13 
13 
13 
13 
14 
13 
Number of scales in transverse series 
15 
36 
14 
35 
15 
33 
14 
33 
14 
33 
14 
33 
14 
37 
15 
36 
15 
34 
15 
36 
16. Tetragonopterus argentatus (Baird & Girard). 
The specimens of T. argentatus from the Rio Verde near Rascon were not more than 55 mm. long. 
The ventral and anal fins were dashed with a bright orange-red and the caudal was tipped with 
orange. A few specimens from the Rio Tamesoe were like those from the Rio Verde, except that the 
fins were not colored. 
