424 DR. GUNTHER ON THE FISHES OF CENTRAL AMERICA. 
one-fifth of the total length. The caudal fin is completely covered with scales, deeply 
forked, with the lobes pointed, the upper one being rather the longer. The distance 
between the caudal and anal fins is less than that between the dorsal and caudal, as the 
extremity of the anal falls behind that of the dorsal, or in the vertical from the forty- 
third scale of the lateral line. Its origin corresponds to that of the dorsal; and it has 
the lower edge straight or very slightly emarginate; it is entirely covered with scales. 
The first two spines are very small, and the third not half the length of the first ray ; 
the first and second rays are the longest, but not twice as long as the fifteeenth or 
terminal ray. The length of the pectoral is not one-fourth of the total; it has minute 
scales towards the base. The free pectoral appendages are six in number; the upper 
one is the longest, reaching to the anal fin, and is not quite one-third of the total 
length. The root of the ventral falls a little behind the middle of the pectoral, and in 
the vertical from the eleventh scale of the lateral line; it is short, one-eighth of the 
total length, reaching to the vent; its spine is more than half the length of the 
adjacent ray. ‘The scales are of moderate size, scarcely higher than long, and minutely 
ciliated on the posterior margin. ‘The lateral line is straight, bifurcating between the 
lobes of the caudal. Teeth on the vomer in a narrow transverse patch. 
Two specimens, 12 inches long, are in the Collection, one found by Mr. Salvin at 
Chiapam, the other by Capt. Dow at Panama. 
Mr. Gill first recognized this species, which is not identical with P. ranthonemus, as 
suggested in the ‘ Catal. of Fishes.’ 
53. PoLYNEMUS OPERCULARIS. 
Trichidion opercularis, Gill, Proc. Acad. Nat. Sc. Philad. 1863, p. 169. 
This fish is described thus :— 
D. 8|/% Aq L. lat. 69-70. L. transv, 8/14, 
The greatest height equals a fourth of the length to the fork of the caudal fin, and 
more than a fifth of the extreme, while the head enters four times and a half in the 
latter. The outline from the dorsal to the snout is nearly rectilinear and little declined. 
The distance of the anal from the outer axil of the ventral equals that of the posterior 
nostril from the margin of operculum. The first dorsal, when bent backwards, rests on 
the fourth scale, in front of the second. The second commences nearly above the 
twentieth scale of the lateral line. The pectoral is as long as the head behind the 
pupil. There are eight pectoral filaments, the longest of which extends rather beyond 
the front of the second dorsal. ‘The colour is greenish brown above and yellowish green 
below. The operculum is blackish. The first dorsal and the pectorals, except below, 
are also blackish, as is likewise the margin of the caudal. The anal is tinged with 
orange. ; 
A single specimen, 11 inches long, was collected by Capt. Dow at Panama. 
