DR. GUNTHER ON THE FISHES OF CENTRAL AMERICA. 477 
and six times and a half in the total. The height of the caudal peduncle equals half 
the interorbital area, and is half its length behind the anal fin. The smooth head 
enters four times in the length to the middle of the central caudal ray, and nearly five 
times in the total. The width of the head enters once and one-third in its length, and 
the width of the interorbital area once and two-thirds. The eye is elliptical, its diameter 
equals a fourth of the head’s length, and the distance from the anterior nostril is equal 
to it. The maxillary barbels extend backwards nearly to the anus, and the mental to 
the bases of the pectoral fins. The dorsal buckler is rather longer than wide, with its 
anterior margin concealed, and its lateral and posterior very conspicuous, rounded 
towards the posterior angles, and emarginated behind; the sides slope and form a 
rectangle, and the surface is filled with deep oblong pits. ‘The anal fin is situated 
midway between, or scarcely in advance of, the central point between the bases of the 
pectoral and caudal fins; it is oblong, and equals or nearly equals the width of the 
head. The pectoral filaments extend about to the middle of the anal fin; the ventrals 
are inserted midway between the lower jaw and base of caudal, and extend backwards 
to the anus, entering twice and a half in the head’s length. The colour above is 
plumbeous; the pectorals thickly dotted with black on their inner faces, and the anal 
less so. 
One specimen, 8 inches long, has been collected by Capt. Dow on the Pacific coast of 
Panama. 
224, PLECOSTOMUS BICIRRHOSUS (Gronoyv. ). 
Messrs. Kner & Steindachner (Abhandl. bayer. Ak. x. p. 60) mention a species of this 
genus from Pacific and Atlantic rivers of Panama, which they regard as a variety of 
Plecostomus bicirrhosus, but which differs in several respects. 
225. CH#TOSTOMUS ASPIDOLEPIS. 
pipe Ae O28 bre G.0 lus lat. 20: 
Head large, depressed, a little longer than broad, its length being contained thrice 
and one-third in the total (without caudal); snout very broad, rounded in front. Inter- 
orbital space nearly flat, with a very slight rising along the middle. Orbit small, its 
diameter being one-third of the width of the interorbital space. Margin of the snout 
granulated. Interoperculum with very few, and for the greater part short, setiform 
spines, the longest of which is about half as long as the orbit. Thorax and belly 
granulated, with naked patches. Dorsal fin higher than long, the length of its anterior 
rays being nearly equal to that of the head; the length of its base equals its distance 
from the hinder axil of the adipose fin. There are seven scutes between the ‘two 
dorsal fins. The pectoral spine is strong, rather longer than the head, covered behind 
with setiform spinules. The ventral fins extend somewhat behind the anal. Twelve 
scutes between anal and caudal. Scutes of the body with a prominent keel, each keel 
