2 ACANTHOPTERYGII. 
b. Two nostrils on each side. 
a, Spinous part of the dorsal fin considerably shorter than the soft-rayed part ; anal with 
lor2spines. 2... ee ee ee eee ee ee 6, SrANIDA. 
8. Spinous part of the dorsal fin not shorter or not much shorter than the soft-rayed part. 
* Ventral fins without scaly axillary processes. 
Two dorsals, with VI-X VII, 8-17 rays; anal with I-I] 6-12 rays . . . . 7. Percip&. 
A single dorsal, with X-XI 10-13 rays; anal with II] 8-l2 rays . . . . 8, CunrRarcHIDé. 
** A scaly process at the base of the spine of each ventral fin. 
A single dorsal with IX 10 rays; anal with II-III 7-9 rays . . . . . . 9. Liocnaraip# *. 
A single dorsal with X-XIV 10-18 rays; anal with II] 7-13 rays. . . . 10. Pomapasip2. 
Two dorsals, with VIII, I 9-11 rays; anal with II] 6-7 rays . . . . . 11. Cuntropomip2. 
In all cases the account of the species is based on an examination of the examples 
in the British Museum Collection; but in the case of groups which have already been 
adequately described a synopsis only is given, with references to the works in which 
more details are to be found. 
Fam. 1. PLEURONECTIDE. 
The Flat-fishes are a large family, at once distinguished from all other fishes by the 
asymmetrical head, with the two eyes on one side. They are mostly marine, but many 
ascend rivers for considerable distances. Jn Mexico and Central America four species 
have been recorded as occurring in rivers above the regions affected by the tides, and 
must therefore be included in an account of the fresh-water fishes. 
1. CITHARICHTHYS, Bleeker, 1862. 
Citharichthys, Jord. & Everm. Bull. U.S. Nat. Mus. xlvii. 1898, p. 2678. 
Kyes on the left side. Mouth moderately large; each jaw with a single series of small pointed teeth ; palate 
toothless. Scales moderate or small, feebly ctenoid, deciduous; lateral line nearly straight. Dorsal 
commencing just in front of the eye and posteriorly free from the caudal; left ventral median, but not 
continuous with the anal; pectorals well-developed. 
1. Citharichthys gilberti, Jenkins & Evermann, 1888. 
Citharichthys gilberti, Jord. & Everm. Bull. U.S. Nat. Mus. xlvii. 1898, p. 2686. 
Depth of body about 2 in the length, length of head 33 to 35. Snout as long as or a little longer than eye, the 
diameter of which is 43 to 53 in the length of head ; interorbital region a narrow, shallow groove, bordered 
by the slightly elevated orbital margins; maxillary extending to below middle of eye; gill-rakers of 
moderate length, 12 to 14 on the lower part of the anterior arch. 38 to 45 scales in a longitudinal 
series. Dorsal 77-85. Anal 57-63. Left pectoral as long or nearly as long as the postorbital part of 
head ; right pectoral shorter ; caudal doubly truncate. Light brown, spotted or marbled with darker. 
Hab. Pacific Coast from Guaymas, Mexico, to Ecuador, entering rivers. 
My description is based on four specimens, 110 to 160 mm. in total length, from 
* Usually known as Gerride, a family name preoccupied in Hemiptera. 
