10 ACANTHOPTEETGII. 



I have examined numerous examples of this form from Presidio, Huamuchal, and 

 Guayaquil, measuring from 110 to 280 mm. in total length. 



4. SICYDIUM, Cuv. & Val., 1837. 



Sicijdhm and Cohjhjms, Jord. & Everm. Bull. U.S. Nat. Mus. slvii. 1898, pp. 2205 & 2207. 

 Oreogobhis, Bouleug. Aun. Mag. N. 11. (7) iv. 1899, p. 12G. 



Eody elongate, suboylindrioal. Mouth wide, subtcrmiual, the lower jaw the shorter ; lips thicdt ; both jaws 

 with a scries of numerous slender teeth, those in the lower jaw horizontal, sometimes completel}' hidden 

 by the gum ; an inner series of erect conical teeth in the lower jaw ; palate toothless. Eyes small or of 

 moderate size ; in terorbital region nioderately broad. Gill-openings of moderate width, nearly vertical, 

 not produced forward below. Scales small, ctenoid. Two dorsals, with VI (V-YII), 1 10-12 rays ; 

 anal with I 9-11 ; caudal rounded ; pectoral symmetrical, rounded ; ventrals united to form a disc 

 which is free from the body posteriorly, with a basal membrane which is folded to form a pit 

 anteriorly. 



In the males the dorsal fins are more elevated than in the females, wliilst the rays 

 of the anterior dorsal are produced into long filaments. 



The genus comprises about thirty species from tropical rivers near the sea, three of 

 which are found in Mexico and Central America. 



1. Sicydium salvini. 



Sicydium salrini, Grant, Proc. Zool. Soc. 1881, p. 159, t. 12. fig. 2\ 

 Sicyopterus salvini, Jord. & Eigenm. Proc. U.S. Nat. Mus. 1886, p. 485 ". 

 Cotylojms salrini, Jord. & Everm. Bull. U.S. Nat. Mus. xlvii. 1898, p. 2208 '\ 

 OreogohiHS rosenbergii, Bouleng. Ann. Mag. N. H. (7) iv. 1899, p. 126 '. 



Horizontal teeth of lower jaw conspicuous. Scales extending forward on the upper surface of head nearly 

 to the interorbital region; abdomen completely covered with small scales; OS to 76 scales in a 

 longitudinal series. Dorsal Yl, I 10. Anal 1 10. iJody with broad irregular darlc cross-bars and with 

 a more or less distinct dark longitudinal band from pectoral to base of caudal ; each scale with a dark 

 spot at the base ; dorsal fins dusky, the second usually with numerous small dark spots, which may 

 unite to form a network ; anal dusky in the male, in the female pale with a dark intramarginal stripe. 



Ilah. Panama i. — Westeisn Ecuadoe '^. 



Here described from five specimens, measuring up to 120 mm., including the types 

 of the species and of 0. rosenhcrgii. 



2. Sicydium gymnogaster. 



Sicydium yijmnogaster. Grunt, Proc. Zool. Soc. 1881, p. 158, t. 11. fig. 2 and t. 12. fig. 6 '. 

 Sicyojjterus gymnogaster, Jord. & Eigenm. Proc. U.S. Nat. Mus. 1886, p. 185 ". 

 CoLyhipus gyvmogusler, Jord. & Everm. Bull. U.S. Nat. ]Mus. xlvii. 1898, p. 2207". 



Horizontal teeth of lower jaw usually more or less completely concealed beneath a tleshy ])ad. Scales not, 

 extending forward on to tho head; abdomen with a median naked area; (30 to 74 scales in a longitudinal 

 series*. Dorsal VI, 1 10. Anal 1 10. (ioloration as iu S. sidvini, but the tins without spots. 



* In three specimens the scales extend forward above (o the level of the gill-opeuing, and in these 1 count 

 GO to 74 in a longitudinal scries. Usually the scales oonimenoe above the peotoral, and consequently this 

 number is fewer. 



