ii8 Field Museum of Natural History — Zoology, 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 diffictilt to capture except with the use of dynamite. The 

 white employees of the United Fruit Company regard this species as 

 the best food fish foimd 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 pterj^goids. 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 rnm.; Virginia (i), no mm.; Zent, April 12 

 (14), 90 to 150 mm.; Zent, April (5), 78 to 120 mm.; Rio Reventazon 

 (i), 300 mm. (Alfaro); El Sardinal, Santa Clara (i), 270 mm. (Alfaro). 



Agonostomus monticola (Bancroft). 



Mugil monticola Bancroft, in Griffith's Ed. Cuvier's Animal King- 

 dom, 1836, 367, pi. 36 (West Indies). 



Agonostomus masutus Regan, Biol. Cent. Amer., 1906, 68, pi. x, 

 fig. 4 (Juan Vinas, Costa Rica). 



Agonostomus percoides Regan, Ann. & Mag. Nat. Hist., 1908, 461 

 (Rio Iroquois). 



These fishes inhabit clear running water and are usually most 

 abimdant in swift currents where there are many rocks. They are 

 very timid, retreating tmder 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 ver>' 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 



