450 
BULLETIN OF THE BUREAU OF FISHERIES 
Figure 64 . — Cypselurus furcatus. From a specimen 5 millimeters long 
ment is far advanced for such a small fish, as some of the adult characters already are 
evident. In general, the state of development in this flyingfish at a length of 5 milli- 
meters is far ahead of most species studied. (Fig. 64.) 
The very oblique mouth, the excessively large eye, and the very prominent dark 
chromatophores that are quite generally distributed over the body are outstanding 
characters. The early development of the fins makes an enumeration of the fin rays 
possible at a remarkably small size. 
Specimens 8 millimeters long. — The head is rather less robust than in specimens 
5 millimeters long, and the body is a little less strongly compressed, the shape and 
form being more nearly as in the adult. The mouth is strongly oblique but less so 
than in smaller fish. The 
fins have developed rap- 
idly; the pectoral fins are 
relatively large and broadly 
rounded, being about twice 
as long as the eye ; the 
ventral fins reach to, or 
a little beyond, the origin of the anal; and the margin of the caudal fin is slightly 
rounded, or more usually nearly straight and oblique, for the lower rays are longer 
than the upper ones. The color remains essentially as in the 5-millimeter specimen. 
(Fig. 65.) 
Specimens 12 millimeters long.- — The principal advancement in development has 
taken place in the fins. The pectorals are notably longer than the head and reach 
nearly or quite to the origin of the dorsal. The ventrals are only slightly smaller 
than the pectorals and reach well beyond the origin of the anal. The margin of the 
caudal fin is straight and strongly oblique, the lower rays being much longer than the 
upper ones. Pigmentation remains about the same as in smaller fish, except that 
the pectorals and ventrals now are dotted with black chromatophores. 
Specimens IS mil- 
limeters long. — The 
body has become more 
robust posteriorly and 
is only slightly com- 
pressed. The mouth 
remains strongly ob- 
lique, and it has be- 
come proportionately 
smaller in size. Two 
dermal flaps about half as long as the eye, not present in the smaller fish, now are 
evident at the tip of the lower jaw. The margin of the caudal fin is concave, and the 
lower lobe is much longer and larger than the upper one. Pigmentation has undergone 
no changes worthy of note since a length of 12 millimeters was attained. (Fig. 66.) 
Specimens 25 millimeters long. — Scales are not evident on specimens 18 milli- 
meters long. Indications of scale pockets are present, however, and at a length of 25 
millimeters scales are well developed although usually lost, as they appear to be loosely 
attached. The pectoral and anal fins have increased in proportionate length, for the 
first-named pair now reaches nearly opposite the middle of the base of the dorsal and 
the other pair reaches to or a little beyond the base of the caudal. These proportions 
are those^attained by these fins in the adult, except that the ventrals in the adult do 
Figure 65 .—Cypselurus furcatus. From a specimen 7.7 millimeters long 
