624 Mr. C. T. Regan on ee 
Trichomycterus retropinnis. 
Length of head 54 times in the total length. Head as 
broad as long. Diameter of eye about 4 times in the inter- 
ocular width, which is 33 times in the length of head. 
Snout as long as the postorbital part of head. Barbels equal 
to about # the length of head. Dorsal with 6 branched 
rays, originating above or slightly behind the anal opening, 
the distance from its point of origin to the caudal 22 times 
in the distance from the former to the tip of the snout. 
Anal with 4 branched rays, originating below the anterior 
third of the dorsal, the distance from the base of its last ray 
to the caudal 52 times in the total length. Longest branched 
ray of the pectoral 2 the length of the simple outer ray, which 
is equal to % the length of head. Ventrals not quite reaching 
the anal opening. Caudal truncate-rounded. Brownish, 
with an indistinct darker stripe along the middle of the side 
and traces of some dark spots. 
Total length 80 mm. 
Two specimens from St. Augustin, Andes of Colombia, 
5000 feet, collected by Capt. Dowding. 
A third specimen, 30 mm. in total length, which I have 
purposely excluded from the above diagnosis, has a well- 
marked broad longitudinal stripe on each side. In it the ~ 
longest branched ray of the pectoral is % the length of the 
outer simple ray, and the distance from the origin of the 
dorsal to the caudal is 24 times in the distance from the 
former to the tip of the snout. 
Allied to JT. nigromaculatus, Blgr., and T. amazonicus, 
Stdr.; in the position of the dorsal fin intermediate between 
the two. 
Trichomycterus meridc. 
Length of head 6-7 times in the total length. Head as 
long as, or longer than, broad. Diameter of eye about 3 times 
in the interocular width, which is about 3 times in the length 
of head. Snout considerably shorter than the postorbital 
part of head, scarcely longer than the interocular width. 
Barbels as long, or nearly as long as the head. Dorsal with 
6 or 7 branched rays, originating a little in advance of the 
anal opening, the distance from its point of origin to the 
caudal 12-14 times in the distance from the former to the tip 
of the snout. Anal with 4 or 5 branched rays, originating 
below the last 2 or 3 rays of the dorsal, the distance from the 
base of its last ray to the caudal 42-5 times in the total 
length. Longest branched ray of the pectoral 3 the length of 
