126 OSTARIOPHYSI. 
Synopsis of the Mexican and Central-American Species. 
I. Middle of eye above the level of the angle of the mouth; 9 to 12 gill-rakers on the lower 
part of the anterior arch. 
A. Anal fin of 19 to 24 rays. 
1. Occipital process not much broader than long. 
a. Teeth on the palate in two rather small, well-separated patches. 
Diameter of eye 6 in the length of head (in specimens of 180 to 200 mm.) ; 
maxillary barbel extending to basal part of pectoral ; dorsal spine 3 the 
length of head ; pectoral spine 2 the length of head, its inner edge very 
strongly serrated . oe ek . we ew ew we he he) CL melanopus. 
Diameter of eye 4 to 5 in the length of head (in specimens of about 180 to 
220 mm.) ; maxillary barbel extending about to base of pectoral ; dorsal 
spine ? to % the length of head ; pectoral spine 3 the length of head. . 2. liropus. 
b. Teeth on the palate in two rather large narrowly separated 
patches; diameter of eye 6 to 74 in the length of head (in 
specimens of 196 to 260 mm.); maxillary barbel extending to 
basal part or middle of pectoral; dorsal and pectoral spines 3 
to 2 the length of head, the latter with the inner edge mode- 
rately serrated 2 1 1. 4 1 6 ew we ew ww we ww we: 8 fucerthii. 
2. Occipital process much broader thanlong. . . . . . . «© « 4. evermanni. 
B. Anal fin of 27 rays ° ® e ° e e ° ° e ry ° ° r) ° 5. multiradiatus. 
II. Middle of eye about on a level with the angle of the mouth; 30 0 gill 
rakers on the lower part of the anterior arch; anal fin of 22 or 
23 rays . 2 6 6 ew ew et we tw ww wt ew ww «6. hypophthalmus. 
1. Arius melanopus. (Tab. XVIII. fig. 1 and Tab. XIX. fig. 7.) 
Arius melanopus, Giinth. Cat. Fish. v. p. 172 (1864) *. | 
Tachysurus melanopus, Jord. & Everm. Bull. U.S. Nat. Mus. xlvii. 1900, p. 2784’. 
Galeichthys aqua-dulce, Meek, Publ. Columbian Mus., Zool. v. 1904, p. 9, t. 4°. 
Depth of body 5 to 54 in the length, length of head 33 to 44. Breadth of head 13 in its length, diameter of 
on, viz., a single nasal opening on each side and a rayed adipose dorsal. Cuvier and Valenciennes (xv. p. 163, 
1840) placed Lacepéde’s fish in the genus Pimelodus and made the following remarks :—‘ M. de Lacépéde a 
cru devoir faire un genre 4 part de ce peisson, 4 cause de quelques traits que l’on voit sur l’adipeuse, et qu'il a 
regardés, dit-il, comme des rayons; ....il le nomme tachisure 4 cause de J’agilité de sa queue, longue et 
déliée, et comme on peut en juger par la copie, assez mauvaise d’ailleurs, qu’il donne de sa figure chinoise, les 
proportions de cette partie ne different pas beaucoup de ce qu’elle est dans les espéces du groupe actuel. Il 
nous parait donc que le genre Tachisure ne peut étre conservé.” 
I have thought it necessary to give in detail the reasons why I use Arius instead of Tachysurus, as the 
latter is now generally used by American ichthyologists, although I am at a loss to imagine how they have 
determined that a fish known only from a Chinese painting had granular or obtusely conical teeth on the 
palate, 
