TETRAGONOPTERUS. 171 
T. eneus is very closely allied to 7. rutilus, Jenyns, which ranges from Venezuela to 
Montevideo, and it is practically impossible to distinguish between young examples of 
the two species. When adult specimens are compared, however, the distance between 
the eye and the upper edge of the lower limb of the preopercle, just behind the arti- 
culation of the lower jaw, is seen to be considerably less in 7. rutidus than in JT. wneus, 
being equal to 4 the vertical diameter of the eye in the former and ? of the same in 
the latter species. 
Steindachner had formerly given the name 7. fischeri to the specimens which he 
described and figured as T. panamensis. Astyanax emperador, Kigenm. & Ogle (Proc. 
U.S. Nat. Mus. xxiii. 1907, p. 26), from Panama, is said to differ from A. fischeri in 
the smaller scales (39 to 45 instead of 34 to 37) in a longitudinal series. 
2. Tetragonopterus macrophthalmus, sp.n. (Tab. XXVI. fig. 4.) 
Tetragonopterus eneus (part.), Meek, Publ. Columbian Mus., Zool. v. 1904, p. 86°. 
Astyanax rutilus, variety ?, Eigenmann & Ogle, Proc. U.S. Nat. Mus. xxxiii. 1907, p. 23 *, 
Depth of body 24 to 32 in the length, length of head 34 to 42. Snout obtuse, decurved, 3 to 2 as long as 
eye, the diameter of which is 23 to 3 in the length of head ; interorbital width 2% to 3 in the length of 
head. Maxillary extending nearly to the vertical from anterior edge of pupil; 0 to 4 maxillary teeth. 
10 to 12 gill-rakers on the lower part of the anterior arch. 34 to 40 scales in a longitudinal series, 6 to 
8 in a transverse series from dorsal fin to lateral line, 5 or 6 between lateral line and base of ventral. 
Dorsal 10-12 ; origin behind the base of ventrals ; longest ray as long as the head; free edge of the fin 
nearly straight. Anal 23-29, of 3 or 4 simple and 20 to 25 branched rays ; free edge usually emarginate. 
Pectoral about as long as the head, usually reaching the ventrals, which nearly or quite reach the origin 
ofanal. Caudal forked. Caudal peduncle longer than deep. Coloration as in the preceding species. 
Hab. Mexico (Sallé), Motzorongo? in Vera Cruz '? (Meek, Gadow). 
Several specimens, measuring up to 150 mm. in total length. 
Mecek’s description is evidently based on examples of this species, but he also had 
the true Z. wneus in his collections. 
3. Tetragonopterus mexicanus. (Tab. XXVI. figg. 2, 3.) 
Tetragonopterus mexicanus, Filippi, Rev. Mag. Zool. 1858, p. 166°; Steind. Sitzungsb. Ak. Wien, 
Ix. 1869, p. 299, t. 4°; Jord. & Everm. Bull. U.S. Nat. Mus. xlvii. 1896, p. 335°; Meek, 
Publ. Columbian Mus., Zool. v. 1904, p. 85°. 
Tetragonopterus argentatus, Baird & Girard, Proc. Ac. Philad. 1854, p. 27°; Jord. & Everm. t. ¢. 
p. 336°. . 
Tetragonopterus fasciatus (part.), Giinth. Cat. Fish. v. p. 322 (1864) *. 
Tetragonopterus brevimanus, Giinth. t. c. p. 825°. 
Tetragonopterus petenensis (part.), Giinth. t. c. p. 826°. 
Tetragonopterus cobanensis, Bocourt, Ann. Sci. Nat. (5) ix. 1868, p. 62°; Vaill. & Pellegr. Bull. 
Mus. Paris, 1908, p. 323”. 
Tetragonopterus oaxacanensis, Bocourt, l.c.??; Vaill. & Pellegr. t. c. p. 324”. 
Tetragonopterus nitidus, Bocourt, l. c.*; Vaill. & Pellegr. 1. ¢.”. 
