144 OSTAKIOPHTSI. 



Syno2)sis of the Mexican and Central-American Sjjecies. 



I. Depth of body 2| to 3r| in the length ; pectoral fin not extending to the ventral. 



A. Dorsal fin of 28 to 31 raj's 1. ineridionaUs. 



B. Dorsal fin of 23 to 26 rays. 



1. Origin of ventrals below about the seventh dorsal ray. 



Depth of body 2J to 3| in the length ; caudal peduncle as long as deep ... 2. microstomiis. 

 Depth of body 85 to 3n in the length; caudal peduncle longer than deep . . 3. elongatus. 



2. Origin of ventrals below about the third dorsal ray 4. labiosiis. 



II. Depth of body about 25 in the length ; pectoral extending to or a little 



beyond the base of ventral 5. tumldus. 



1. Ictiobus meridionalis. (Tab. XXIV. fig. 1.) 



Scleroffnathus 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 2| to 3^ in the leugth, length of head 4 to 4^. Diameter of eye Ij iu the length of snout 

 and .5g in the length of head ; interorbital width 2 to 2\ in the length of head. Snout obtuse, more or 

 loss 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 |- to | of the distance from its base to the origin of the ventral, which is below tho 

 fourth to sixth rays of the dorsal. Caudal emargiuate. Caudal peduncle nearly as long as deep. 

 ISilvery, back brownish. 



llat). Mexico, Perez in Vera Cruz^ [Meek) ; Guatemala, 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. Coluiubian Mus., Zool. v. 1904, p. 27, fig. 4 '. 

 llaJ). Mexico, Rio Conchos in Chihuahua ^. 



Four small specimens from the Rio Conchos [Meek) differ from /. meridionalis 

 especially in the shorter dorsal fin. 



3. Ictiobus elongatus. 



Carpiodes eloufjatus, Meek, Publ. Columbian Mus., Zool. v. 1904, p. 28, fig. 5 '. 



Ifah. Mexico, Rio San Juan, Rio Conchos, and Rio Soto Marina in Tamaulipas '. 



