FISHES FROM THE RIVERS OF MEXICO. 
141 
caudal, very small and crowded together; those in the region of dorsals not reduced in size nor 
crowded except at insertion of fins, where there are 4 very small ones; cheeks with 5 rows; lower 
jaw and upper part of snout naked; basal half of interradial membranes of caudal with minute 
scales. First 3 spines of dorsal highest, extending when depressed within half their length of origin 
of soft dorsal; first dorsal ray preceded by a shorter, simple, closely attached one; other rays succes- 
sively shorter than first; edge of fin slightly concave; anal similar to soft dorsal in shape, its basis 
1.66 times as long as that of soft dorsal; attachment of first ray under a point halfway between 
insertions of dorsals; caudal deeply forked, the lobes equal; pectorals pointed when depressed; upper 
rays longest, extending to a vertical, halfway between insertions of first dorsal and ventrals. 
Body, during life, almost translucent, with a bluish tinge of color. In alcohol the color is a light 
olive-yellow; a silvery lateral band extending from axil to base of caudal, the band wider and 
brighter in color between dorsal and anal, growing narrow on caudal peduncle and then widening 
again at its posterior end; head and body above, and the lower jaw dusky; upper part of eye dark; 
edges of scales above lateral band with small black dots; caudal somewhat dusky on its basal third; 
other fins with little or no dark color. 
Chirostoma ocotlane is easily distinguished from all other kuown species of the genus by its 
excessively long lower jaw. Except the jaw and somewhat larger eye it resembles C. estor* in general 
appearance. The following gives some exact measurements of the type and also shows some slight 
individual variations. 
Measurements of ten specimens of Chirostoma ocotlane. 
Measurements. 
Laguna de 
Chapala. 
Guadalajara market, said to have come from 
Laguna de Chapala. 
Length of body in millimeters 
160 
191 
210 
193 
193 
192 
182 
177 
174 
155 
Depth of body expressed in hundredths 
of length 
24 
22 
22 
21i 
23 
23 
23 
214 
21 
18 
Depth of caudal peduncle 
9* 
8* 
8i 
9 
9 
9 
94 
9 
9 
84 
Length of head 
31 
31 
32i 
29A 
32 
32 
32 
32 
32 
32 
Distance from snout to occiput 
224 
22i 
23 
2H 
221 
23 
224 
23 
23 
22i 
Tip of lower jaw to occiput 
26 
26 
27 
25 
26 
26i 
26 
264 
264 
20 
Width of interorbital space 
6 
6i 
7 
6 
6 
(5 
6 
7 
6 
54 
Length of snout 
lli 
11 
12 
11 
12 
12 
12 
12 
12 
Hi 
Diameter of orbit 
7 
GW 
6£ 
6i 
7 
6i 
64 
7 
6 
7 
Distance from snout to spinous dorsal.. 
56 
56J 
56 
56 
56i 
57 
564 
554 
55 
554 
Insertion of spinous dorsal to soft dorsal . 
13i 
12 
13 
13 
12 
124 
12 
124 
134 
124 
Height of longest dorsal spines 
9 
9 
8i 
8* 
84 
7i 
8 
9 
8 h 
8" 
Height of longest dorsal rays 
15 
141 
13i 
14 
14i 
13i 
14 
154 
15 
15 
Distance from snout to anal tin 
634 
65 
66 
654 
65 
63 
64 
64 
654 
04 
Height of longest anal rays 
16 
36i 
15 
15 
16 
15i 
16 
17 
15 
16 
Distance from anal to caudal tin 
20 
17i 
194 
18 
19 
18 
19 
184 
184 
19 
Length of caudal fin 
22 
22 
22 
21 
24 
21i 
214 
23 
224 
22 
Length of pectoral fin 
194 
21* 
21i 
19 
20 
20 
194 
22 
21 
21 
Distance from snout to ventral fin 
48 
50 
51 
48 
50 
484 
50 
48 
49 
49 
Length of ventral tin - 
12 
12 
13 
12i 
12 
11 
13 
134 
124 
12 
Number of spines in first dorsal 
5 
5 
5 
5 
5 
5 
5 
5 
5 
5 
Number of rays in second dorsal 
12 
12 
11 
12 
12 
12 
12 
12 
12 
12 
Number of rays in anal 
20 
20 
19 
21 
19 
22 
21 
20 
21 
21 
Number of rays in pectoral 
15 
15 
15 
15 
15 
15 
15 
15 
15 
15 
Number of scales in lateral line 
54 
56 
55 
54 
56 
57 
53 
53 
57 
57 
Number of scales in transverse series. . . 
19 
18 
18 
19 
18 
20 
18 
19 
18 
17 
N umber of scales bet ween dorsals 
11 
11 
11 
10 
12 
13 
12 
10 
11 
12 
* We have reexamined the type specimen of Chirostoma estor. The scales are small and closely 
crowded on the region anterior to the pectorals from the occiput to the isthmus ; they are not much 
reduced in size nor closely crowded together between the dorsals. The teeth on the jaws are large 
and numerous; not arranged in definite rows; 3 vomerine teeth almost as large as those on jaws. 
Some measurements of the type of C. estor expressed in hundredths of length of the body, are 
here given: Length of body in millimeters 212; depth of caudal peduncle 7.5; length of head 31.5; 
distance from snout to occiput 23 ; tip of lower jaw to occiput 24; widtli of interorbital space 7 ; length 
of snout 12; diameter of orbit 5.66; distance from snout to spinous dorsal 56.5; insertion of spinous 
to soft dorsal 12.5; height of longest dorsal spines 7; of longest dorsal rays 11; distance from snout 
to anal 62.5; height of longest anal rays 12; distance from anal to caudal 22; length of caudal fin 
18.5; of pectoral fin 17; distance from snout to ventral 45.5 ; length of ventral fin 10.5; D. v-12; A. 18; 
P. 14; scales 72-19, 9 between the dorsals. 
The type of Chirostoma estor agrees externally almost perfectly with Steindacliner’s account of 
Chirostoma album from Lake Patzcuaro, a species which he later places in the synonymy of C. estor. 
But the type localities are widely separated, and Steindachner found no trace of the large vomerine 
teeth so conspicuous in C. estor. We therefore regard 0. album as probably a valid species not 
identical with C. estor. 
