144 OSTARIOPHYSI. 
Synopsis of the Mexican and Central-American Species. 
I. Depth of body 2? to 3% in the length; pectoral fin not extending to the ventral. 
A. Dorsal fin of 28 to 3lrays . . 1. 1. 1. ee ee ee OL meridionalis. 
B. Dorsal fin of 23 to 26 rays. 
1. Origin of ventrals below about the seventh dorsal ray. 
Depth of body 22 to 34 in the length; caudal peduncle as long as deep . . . 2. microstomus. 
Depth of body 3} to 32 in the length; caudal peduncle longer than deep 
ie) 
. elongatus. 
2. Origin of ventrals below about the third dorsalray . . . . . . 4. dabiosus. 
II. Depth of body about 23 in the length ; pectoral extending to or a little 
beyond the base of ventral. . 2. 2. 2. 2. ew. 1 ew we ee OBL tumidus. 
1. Ictiobus meridionalis. (Tab. XXIV. fig. 1.) 
Sclerognathus meridionalis, Giinth. Cat. Fish. vii. p. 23 (1868) *. 
Ictiobus meridionalis, Jord. & Everm. Bull, U.S. Nat. Mus. xlvii. 1896, p. 164°. 
Carpiodes meridionalis, Meek, Publ. Columbian Mus., Zool. v. 1904, p. 26°. 
Depth of body 22 to 33 in-the length, length of head 4 to 44. Diameter of eye 13 in the length of snout 
and 53 in the length of head; interorbital width 2 to 27 in the length of head. Snout obtuse, more or 
less projecting beyond the mouth, which has plicated lips. 36 to 40 scales in a longitudinal series, 
7 or 8 in a transverse series from origin of dorsal fin to lateral line, 5 or 6 between lateral line and base 
of ventral. Dorsal 28-31, the 3 anterior rays simple, the fin elevated anteriorly, the longest ray shorter 
than the head. Anal 10, the 3 anterior rays simple, the fin, when laid back, extending to the caudal. 
Pectoral extending 2 to 3 of the distance from its base to the origin of the ventral, which is below the 
fourth to sixth rays of the dorsal. Caudal emarginate. Caudal peduncle nearly as long as deep. 
Silvery, back brownish. . 
Hab. Mexico, Perez in Vera Cruz* (Meek); Guatemaua, Rio Usumacinta (Salvin) !. 
Here described from the types, four specimens, 200 to 250 mm. in total length, 
with which I have compared two small specimens from Perez. This species is said to 
attain a length of over 600 mm. 
2. Ictiobus microstomus. 
Carpiodes microstomus, Meek, Publ. Columbian Mus., Zool. v. 1904, p. 27, fig. 4'. 
Hab. Mexico, Rio Conchos in Chihuahua !. 
Four small specimens from the Rio Conchos (Meek) differ from J. meridionalis 
especially in the shorter dorsal fin. 
8. Ictiobus elongatus. 
Carpiodes elongatus, Meek, Publ. Columbian Mus., Zool. v. 1904, p. 28, fig. 51. 
Hab. Mrxico, Rio San Juan, Rio Conchos, and Rio Soto Marina in Tamaulipas |. 
