XXI OSTARIOPHYSI 595 
Callichthys. There are other sexual differences in many species 
of Plecostomus, Chaetostomus, and Loricaria, as the presence of 
dermal tentacles on the snout (see Fig. 359), or of hair-like 
bristles on various parts of the head and fins in the males, which 
are usually of larger size. 
About 200 species are known, all from the tropical and sub- 
tropical parts of Central and South America. The largest species 
(Chaetostomus gigas) measures 24 feet; many are of very small 
size! The genera may be referrl to two sub-families -— 
G.) ARGINAE—Body naked; ribs strong. Arges, Stygogenes, 
Astroblepus. 
Qi.) LORICARIINAE.—Body cuirassed by bony plates; ribs very 
slender. Plecostomus, Liposarcus, Chaetostomus,  Cochliodon, 
“Pterygoplichthys, Rhinelepis, Acanthicus, Otocinclus, Hypopto- 
poma, Loricaria, Acestra. 
Se LU, a 
Fic. 360.—Acestra gladius, from the Jurua River, with upper and lower views of 
head and trunk. (2 nat. size.) 
° 
The “Prenadillas” of the Andes, Arges and Stygogenes, were 
believed to live in subterranean waters within the bowels of active 
volcanoes, and to be ejected with streams of mud and water during 
eruptions, a story that has been repeated by Humboldt. The 
fact is that they live in small torrents at great altitudes (up to 
10,700 feet), and are swept down during periods of disturbance 
caused by the eruption of the voleano.” The members of the sub- 
family Loricariinae vary much in the shape of the body, which 
may be short and stout, or more or less slender, the extreme in the 
latter respect being attained by the species of the genus Acestra. 
1 A monograph of these Fishes, by Mr. C. T. Regan, will shortly appear in the 
Transactions of the Zoological Society. 
2 Cf. Moritz Wagner, Abh. Akad. Miinch. x. 1866, p. 101, and Whymper, 7’7rav. 
Andes Ecuador, 1892, p. 251. 
