184 
U. S. P. R. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
PHANERODON FURCATUS, Qrd. 
Plate XXXIY, Figs. 1—5. 
Spec. Char. —General form elongated, rather tapering posteriorly, and very much compressed. Cleft of mouth not extending 
to the anterior rim of the orbit. Eyes large and circular. Branchiostegals five in number. Caudal slender and deeply forked. 
About sixty-three scales in lateral line. Yellowish brown above ; lighter on the sides ; whitish under the throat. Fins yellowish. 
Margin of dorsal and caudal greyish. A diffused marginal spot upon the anterior portion of anal. 
Syn. —Plianerodon furcatus, Grd.' in Proc. Acad. Nat. Sc. Philad. VII, 1854, 153 ; and, VII, 1855, 322. 
The general form of the body has a rather elongated appearance, posteriorly tapering towards 
a slender caudal peduncle, which terminates into a slender and deeply forked fin. It is very 
much compressed. The head, which constitutes about the fifth of the length, is rather small, 
slightly depressed above the eyes. The snout is abbreviated and rounded ; the mouth small, 
and the teeth, proportionally large, are disposed upon one single row on either jaw ; about 
twelve on the upper and fourteen on the lower, occupying most of the circumference of the 
mouth. The lips are well developed, but quite thin, and the frenum which unites the lower 
one to the symphysis of the jaw is exceedingly narrow, and might easily be overlooked. The 
premaxillaries are very protractile ; the jaws are perfectly even when the mouth is closed. 
The posterior extremity of the maxillaries do not quite reach a vertical line passing immediately 
in advance of the anterior rim of the orbit. The eye is large, circular, and its diameter com¬ 
prised about three times and a half in the length of the side of the head, exactly once in 
advance of its anterior edge. The anterior nostril is placed about midway between the orbit 
and the extremity of the snout. The branchiostegal rays are five on either side, the inferior one 
being exceedingly slender. A vertical line drawn from the origin of the dorsal fin intersects 
the middle of the base of the pectorals. The spinous portion of that fin is gradually rising 
from the first to the last spine, which is a little shorter than the first articulated ray, whence 
the fin again diminishes in height towards the last articulated ray. The soft portion is one- 
third longer on its base than the spinous ; the articulated rays are slender, and bifurcate but 
once beyond the middle of their length. The caudal fin, which is contained about four times 
and a half in the total length, is deeply forked, and provided upon the base of its rays with 
small and irregularly arranged scales. The rays divide three times, the central ones only 
twice. The anal fin is long and low ; its base is contained four times in the total length, and, 
consequently, longer than the base of the soft portion of the dorsal, which enters in the total 
length about four times and a half. Its external margin is slightly concave upon its middle. 
The anterior spines are slender and well developed, the third being nearly as long as the last 
articulated ray. About nine of the anterior articulated rays are undivided ; the others bifurcate 
once like those in the dorsal fin. The tips of the ventrals extend as far as the first anal spine ; 
their insertion is under the vertical line of the third dorsal spine. The articulated rays of these 
fins bifurcate twice. The pectorals are long and slender, extending backwards to a vertical 
line which would intersect the fourth articulated ray of the dorsal and the second anal spine. 
Their rays bifurcate twice. 
The formula of the fins is as follows : 
Br. Y: Y; D XI, 24; A III, 9 + 23 = 32; C 3, 1, 6, 6, 1, 2 ; Y I, 5 ; P 18. 
