172 OSTAEIOPHTSI. 



Tetragoiiojiierus fulfjens, Bocourt, 1. c.'" ; Vaill. & Pellegr. 1. c". 

 Tetragonupttrus streetsii, Cope^ Proc. Ac. Philad. ISTl, p. 217 ". 

 Astyauax mcxicaims, Eigeumami & Ogle, Bull. U.S. Nat. Mus. xxxiii. 1007, p. 25 ". 



Depth of bod}- 2| to 3^ in the length, length of head 33- to 4|-. Snout obtuse, nearly as long as or shorter 

 than eye, the diameter of which is 2| (young) to 3^ in the length of head ; interorbita] width 2^ to 2-i 

 in the length of head. Maxillary extending about to the vertical from anterior edge of pupil, or 

 sometimes nearly to below middle of eve; maxillary teeth to 5. 10 to 14 glll-raliers on the lower 

 part of anterior arch. 33 to 39 scales in a longitudinal series, 6 to 8 in a transverse series from 

 dorsal fin to lateral line, 4^ to 7 between lateral line and root of ventral fin. Dorsal 10-12; origin 

 above or a little behind the base of last ray of ventral ; longest ray ^ to ^ the length of head; free 

 edge of the fin straight or slightly convex. Anal 20-27, with 3 or 4 simple and 17 to 24 branched 

 rays, free edge usually slightly emarginate. Pectoral f to I the length of head, sometimes reaching 

 the ventrals, which may or may not extend to the origin of anal. Caudal forked. Caudal peduncle 

 longer than deep. Olivaceous above, silvery below ; a bluish-silvery lateral band ; often a dark humeral 

 blotch ; an oblong blackish spot on the caudal peduncle, extending to the end of the middle caudal rays. 



Ilah. Texas 1^, Eio Grande'^, Eio Nueces^ [Smithsonian Inst.), and Rio Leona^. — Mexico, 

 Rio Conchos in Chihuahua ^ ( IFoohnan), Rio Nazas in Durango ■^, Rio San Juan in 

 Isuevo Leon"*, Rio Conchos, Rio Soto Marina, and Rio Fodon in Tamaulipas * 

 [Meek), Rio Verde in San Luis Potosi '^ [Jordan, Meek), Rio Papaioapam and its 

 tributaries "* ^^ ; Rio Balsas and its tributaries i 2 4 i4 is i6 n [Jjoitcard, Meek) ; 

 Guatemala, Rio Chisoy ", Rio San Geronimo ^, Lake Peten ° and Lalce Yzabal ^ 

 [Sahin), Coban in Vera Paz 1° " [Paris Mus.). 



Here described from a large series of specimens measuring up to 120 mm. in 

 total length, including the types of T. hrevimanus (fig. 3) and T. 2)etenensis (fig. 2), 

 co-types of T. argentatus and of T. cohanensis, and examples collected at Cuernavaca 

 by M. Boucard, corresponding to the T. nitldus and T. faJgens of Bocourt, which were 

 described from specimens obtained at this place by the same collector. 



4. Tetragonopterus angustifrons, sp. n. (Tab. XXVI. fig. 5.) 



Depth of body about 3 in the length, length of head 3j to 4. Snout subconioal, g as long as eye, the 

 diameler of which is 3 in the lengtli of head; intcrorbital width 3g to Si in the length of head. 

 Maxillary extending about to the vertical from anterior edge of pupil ; 3 to 5 maxillary teeth. 14 to 17 

 gill-rakers on the lower part of the anterior arch. 34 to 38 scales in a longitudinal series, 7 or 8 in a 

 transverse series from dorsal fin to lateral line, 6 or 7 between lateral lino and base of ventrals. Dorsal 

 11 ; origin behind the base of ventrals ; longest ray 5 to i the length of head ; free edge of fin shghtly 

 convex. Anal 2G-29, of 3 or 4 simple and 23 to 20 branched rays; free edge slightly emarginate. 

 Pectoral ^ the length of head, about reaching the ventrals, which extend nearlj^ to the anal. Caudal 

 forked. Caudal peduncle longer than deep. Coloration as in the preceding species. 



Eah. Mexico [Salle). 



Three specimens, the largest SO mm. in total length. 



6. CHIRODON. 



Cliirodori, Girard, Proc. Ac. Philad. vii. 1854, p. 199; Giiatli. Cat. Fish. v. p. 3;i2 (1861). 

 About twelve species from South America and one from Mexico. 



