150 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
of opercle to eye equaling distance from tip of snout to posterior edge of pupil; upper jaw protractile; 
lower jaw prominent, very oblique, including upper jaw; a row of small villiform teeth on each jaw; 
dorsal outline dropping downward and backward along base of fin, thence backward and but slightly 
downward to base of caudal; caudal truncate; lower profile similar to dorsal, though not so greatly 
arched. Color in alcohol, dusky grayish, the central portion of each scale in some cases being dark 
olivaceous, making bands on each row of scales on side of body; belly and neck silvery white; 8 or 9 
bands of dark about as wide as pupil, but irregular in width, on side of body; fins all dusky pale. 
20. Belonesox belizanus Kner. 
Three specimens, 4.2 to 5 inches long, from Progreso, Yucatan. Head 3 (2.75 to 3); depth about 
6; eye 6 (5.5 to 6); snout 2.25; mandible 1.8 to 2; interorbital 3.8; scales 55 or 60,-16 or 17, about 6 
rows on cheek; D. 8, the longest ray 3 in head; A. 10, the longest ray 2.8; ventrals 3.8; pectoral 2.8. 
Body very oblong, compressed posteriorly; head and anterior portion of body flat; head long, very 
flat above, the snout wedge-shaped; eye high; distance from tip of snout to anterior edge of eye 
equaling distance from center of pupil to posterior edge of opercle; upper surface of premaxillary plate 
not quite as long as postorbital part of head; upper jaw protractile, the premaxillaries forming together 
an elongate triangular plate, the bones separated by membrane; lower jaw long, projecting slightly 
beyond upper; mandibles formed similarly to premaxillaries; jaws arched, each with a broad band of 
cardiform teeth; dorsal placed far posteriorly; caudal rounded; anal in advance of dorsal, modified in 
the male into a long, slender intromittent organ. General color in alcohol, dark olivaceous, darker 
above; side with longitudinal series of dark spots, the spots on the posterior central portion of each 
scale; a dark spot, slightly larger than pupil, just above the central base of caudal; caudal dusky 
pale with numerous dark punctulations; other fins dusky pale. 
21. Anableps dovii Gill. “ Quatro Ojos ” ; Four-eyed Fish. 
We have examined 2 specimens of this interesting fish, 7 and 8 inches long, respectively, collected 
by Mr. Nelson in the Tehuantepec River at Tehuantepec City. Head 4; depth 6.25; eye 4.5; snout 
3.75; interorbital 4; width of mouth 2.5; dorsal 8; anal 8; scales, 67,-15; pectoral 1.5; ventral 2.3; 
anal 2.4; dorsal 2.4; middle caudal rays 1.4. Body long, much depressed on anterior half, posterior 
half somewhat compressed; head broad, very greatly depressed; mouth small, the maxillary and 
mandible short, the cleft not nearly reaching anterior border of eye; eye large, set very high, fully 
one-half being above the level of the low interorbital space; fins all small; dorsal posterior, its origin 
over tip of anal; caudal rather long, rounded; ventrals short, wide apart, not reaching vent; pectorals 
short, reaching only halfway to base of ventrals; scales small, smooth, and moderately firm. 
Color in alcohol, brownish olive on back and upper part of side, pale below; median line of back 
with an obscure blackish band; a distinct black band from eye along middle of side to base of caudal 
peduncle, its lower boundary very distinct, in contrast with the paler color of lower side; a similar but 
paler dark line from above base of ventral to base of caudal, the pale yellowish line between these two 
scarcely equal to diameter of eye in width; in some cases this second dark line begins under tip of 
pectoral; dorsal and caudal dusky, other fins pale; tip of upper jaw dark; peritoneum black. 
The unique structure of the eye of this curious fish merits a fuller description. Mr. M. C. Marsh, 
pathologist of the Commission, has made careful dissections of the eye of this species and kindly 
furnishes us the following notes: 
The eye is crossed by a bar, like the diameter of a circle, and parallel with the length of the body. 
This bar is darker than the other external portions of the eyeball and has its edges darker still. Divid- 
ing the external aspect of the eye equally, it has its lower edge on the same level as the back of the 
fish, which is flat and straight from snout to dorsal, or nearly the whole length of the fish; so that when 
the body of the fish is just submerged the level of the water reaches to this bar, and the lower half of 
the eye is in water, the upper half in the air. Upon dissecting the eyeball from the orbit, it appears 
nearly round. A membranous sheath covers the external part and invests most of the ball. It may 
be peeled off, when the dark bar on the external portion of the eye is seen to be upon this membrane, 
which may correspond to the conjunctiva. The back portion of eyeball being cut off, one lens is found. 
The lining of the ball consists, in front, of one black layer, evidently choroid. Behipd, there is a retinal 
layer. The choroid layer turns up anteriorly, making a free edge comparable to an iris. The free edge 
is chiefly evident in the lower part of the eye. A large pupil is left, but is divided by two flaps, con- 
tinuations of the choroid coat, projecting from either side and overlapping. There are properly then 
two pupils, an upper and lower, separated by a band consisting of the two flaps, which may probably, 
