470 DR. GUNTHER ON THE FISHES OF CENTRAL AMERICA. 
also closely allied to Etroplus, which genus, however, has but a rudimentary lateral line, 
whilst in Neetroplus it, is as much developed as in Heros. 
190. NEETROPLUS NEMATOPUS. (Plate LX XIV. fig. 4.) 
D. = A.3. L. lat. 34. L. transv. 54/12. 
The fold of the lower jaw interrupted in the middle; five series of scales on the 
cheek. Incisors a The outer ventral ray produced into a filament as long as the fin. 
One specimen, 43 inches long, was discovered by Capt. Dow in Lake Managua. 
Description —The height of the body is contained twice and three-fifths in the total 
length (without caudal), the length of the head thrice and two-fifths. Head as high as 
long, with an adipose prominence over the eye, which renders the profile of the fore- 
head somewhat abrupt; snout rather compressed and prominent, the length of the 
snout is two-fifths of that of the head, and more than the width of the orbit, which is 
nearly one-third of the length of the head. Cleft of the mouth small, extending back- 
wards somewhat behind the vertical from the nostril; jaws equal in front; teeth im a 
band, those of the outer series being genuine incisors, which appear to be replaced by 
smaller ones, standing behind in a band. Preeorbital wider than the eye, equal in width 
to the interorbital space, which is convex. The eye is situated at some distance from 
the upper profile, nearer to the end of the opercle than to that of the snout. Scales on 
the cheek small, in about five oblique series. Posterior limb of preoperculum about 
twice as long as the inferior, and descending obliquely forwards. Scales on the 
opercles as large as those on the neck; those near the base of the dorsal and on the 
abdomen very small. The dorsal fin commences above the vertical from the hinder 
margin of the operculum. Dorsal and anal scaly at the base. Spines rather strong, 
the sixteenth dorsal spine being nearly one-half of the length of the head. The soft 
portions of both fins are produced, and reach beyond the middle of the caudal. Caudal 
truncated. Pectoral shorter than the head. Outer ray of ventral produced into a 
filament as long as the fin. Brownish-olive, with irregular darker clouds. 
MIcRODESMUS. 
Ginth. Proc. Zool. Soc. 1864, p. 26. 
Body much elongate, eel-like, covered with rudimentary scales. Head rather short, 
with snout obtuse, cleft of the mouth narrow, and lower jaw prominent. Eyes minute. 
Teeth in both jaws minute; palate toothless. The gill-opening is reduced to a small 
slit in front of the pectoral fin. Vertical fins united by a membrane; but the caudal 
can be easily distinguished from the two other fins. Dorsal fin very long, composed of 
flexible, undivided rays, like the anal. Pectorals short; ventrals thoracic, each reduced 
toa single ray. Vent in the middle of the total length. 
Tam not able at present to add anything to the knowledge of this fish which would 
elucidate its natural affinities and indicate its systematic position. 
