- Gn the Collection of the British Museum... 477 
length being more than one-third of the total (without caudal). 
The horizontal diameter of the orbit is more than one-half of 
the width of the interorbital space, and about one-fifth of the 
length of the head. Margin of the snout granulated, without 
bristles ; interoperculum with a bundle of about twenty seti-. 
form spines, the longest of which are about one-fourth of the 
length of the head, and extend backwards to the root of the 
toral fin. Thorax and belly entirely naked. Twelve scutes 
tween the anal and caudal fins. Scutes of the body without 
keels, but with vertical series of spines, the anterior scutes 
with one series only, the middle with two, and the posterior 
with three or more. Blackish brown; head and body with 
numerous indistinct round yellowish spots, each about as large 
as the ee each dorsal ray with a series of round whitish 
spots, the black ground-colour forming a network on the fin, 
. Surinam, 
Cheetostomus dentex. 
. ao with a bundle of about ten straight setiform 
spines, the longest of which is as long as the eye. ‘Thorax 
and belly nearly entirely naked, there being only a few granu- 
lations behind the throat. Teeth comparatively large, with 
the apex dilated, scarcely lobed; there are about six on each 
side in the upper jaw, and three in the lower. Scutes not 
ony but savured with strong spines. Uniform greyish 
rown. 
Xeberos. ? 
HyYPopropoMA (g. n. Hypostomatin.). 
- This genus differs from Plecostomus in the peculiar forma- 
tion of the head, which is depressed, spatulate, the eyes being 
on the lateral edge of the head. ‘The moveable gill-covers are 
reduced to two bones, viz. :—the operculum, small and placed 
as in Plecostomus ; and a second, larger bone (interoperculum ?), 
separated from the eye by the narrow suborbital ring, and 
placed at the lower side of the head. : 
Hypoptopoma thoracatum. 
De Pi. A. 6. 'P. 1/6. V. 1/5, Li lat. 24. 
Xeberos. 
Loricaria lanceolata. 
Head and body much depressed, but narrow, the greatest 
width of the head being three-fifths of its length. Lower lip 
broad, slightly notched behind, fringed. ‘Teeth very fine, few 
in number, about five on each side in the upper jaw, and about 
seven in the lower. Orbit with a rather shallow notch behind, 
its horizontal diameter (the notch included) being two-thirds 
