118 Frerp Museum or Natura History — Zo6iocy, VoL. X. 
Xenorhynchichthys stipes Regan, Ann. & Mag. Nat. Hist., 1908, 461 
(Rio Iroquois). 
The young of this species has two oblique black bands on each lobe 
of the caudal and two similar ones on the soft dorsal and anal fins. 
Large examples, 270 mm. and up, are darker in color, the fins being the 
color of the body except lighter on distal portion. These larger examples 
have a prominent tubercle on the upper edge of the snout, which is 
probably used to turn stones to obtain crustaceans and insects upon 
which they feed. These fishes are abundant in the rocky streams of 
Costa Rica, and especially so at the foot of. rapids and waterfalls. 
They are difficult to capture except with the use of dynamite. The 
white employees of the United Fruit Company regard this species as 
the best food fish found in the Costa Rica rivers. It is reported to 
reach a length of 3 feet, but the largest obtained by us at La Victoria were 
about 2 feet in length. These largest specimens I did not preserve. 
The specimens, large and small, examined by me have teeth on the 
vomer, palatines and pterygoids. Mr. Hildebrand kindly examined 
the type of Joturus stipes Jordan and finds teeth also on the palatines. 
This species varies greatly especially with age. It is generally known 
throughout Central America as Bobo. 
Victoria (5), 55 to 320 mm.; Virginia (1), r10 mm.; Zent, April 12 
(14), 90 to 150 mm.; Zent, April (5), 78 to 120 mm.; Rio Reventazon 
(1), 300 mm. (Alfaro); El Sardinal, Santa Clara (1), 270 mm. (Alfaro). 
Agonostomus monticola (Bancroft). 
Mugil monficola Bancroft, in Griffith’s Ed. Cuvier’s Animal King- 
dom, 1836, 367, pl. 36 (West Indies). 
Agonostomus masutus Regan, Biol. Cent. Amer., 1906, 68, pl. x, 
fig. 4 (Juan Vifias, Costa Rica). 
Agonostomus percoides Regan, Ann. & Mag. Nat. Hist., 1908, 461 
(Rio Iroquois). 
These fishes inhabit clear running water and are usually most 
abundant in swift currents where there are many rocks. They are 
very timid, retreating under rocks or overhanging banks when in the 
least disturbed. In general, the smaller specimens have thin lips and 
a terminal or subterminal mouth. Apparently with age the lips thicken 
and the lower jaw shortens and becomes subinferior. It is very probable 
that most, if not all, of the American species referred to this genus are 
the same, the variations being due to age and probably to sexual differ- 
ences. The larger specimens are very difficult to collect except with 
