237 
PIMELODUS CINERASCENS, n. sp. (PI. X. fig. A.) 
Bias D. 6.) Ae oN. Ya. SP. 1/9. 
The body is somewhat elongated, compressed posteriorly. Head 
broad, truncated anteriorly, depressed, rather short; its length is 
contained four times and three-fifths in the total length of the fish. 
The snout is short, one-third the length of the head, truncated, with 
the upper jaw slightly longer ; the distance between the angles of the 
mouth is nearly one-half the length of the head. Six barbels: that 
of the maxillary reaches nearly to, or somewhat beyond, the base of 
the ventrals ; the exterior pair of the mandibulary barbels is not quite 
twice as long as the interior, and extends beyond the base of the 
pectorals; the interior pair are inserted somewhat before the outer 
ones, and more remote from each other than from the outer ones. 
The eye is distant from the snout two and a half of its diameters, and 
four from the extremity of the operculum ; the width of the inter- 
orbital space is contained twice and two-thirds in the length of the 
head. The head is covered superiorly with a thin, smooth skin ; 
the occipital process is rather short, hidden by the skin, and the 
notches on its side are moderately deep and semicircular. The lower 
margin of the operculum is straight, not notched. The depth of 
the body, taken above the origin of the anal, is one-eighth of the 
total length; that of the tail, before the caudal, one-thirteenth. 
The pectoral extends somewhat beyond the vertical from the origin 
of the dorsal ; its spine is stout, compressed, not much shorter than 
the soft rays, and its sharp outer edge is armed with recurved spines. 
The ventral, with a feeble spine, is inserted behind the dorsal, and 
does not extend to the origin of the anal. The distance of the dorsal 
from the head (concavity of the notch) equals the length of its base ; 
its spine is feeble; the margin straight, rounded posteriorly. The 
adipose fin is very long, its distance from the dorsal and caudal 
being equal. Caudal deeply notched, with the lobes rounded. The 
length of the base of the anal equals its distance from the caudal ; 
the undivided rays are very feeble, and its margin is rounded. 
Above uniform greenish-grey, beneath white; the outer parts of 
the vertical fins are blackish, and there is a blackish spot between 
the first and second dorsal rays. 
Hab. Fresh waters of Guayaquil and Esmeraldas 
inches. lines. 
Gar Wea att oad Gal occa ie os a 98 6 
Length of the head ...... See He be 9, 
GE GUC MOIR. Be ose hint ets 4 Ol oy O 
Distance between the eyes ............-. Maas 
between the angles of the mouth.. 0 9 
Diameter of the eye .......... a lc bra s I an 
Height of the body above the anal........ 0 il 
CNR ales om cle iece ony Sagal ert OL jas 
This species is distinguished from P. seb@ by the position of the 
eyes, shorter maxillary barbel, &c.; from P. pentlandii by a non- 
emarginated operculum. 
