Part I.— DESCRIPTIVE CATALOGUE OF THE FISHES OCCURRING 
IN THE FRESH WATERS OF EL SALVADOR 
All of the fishes of the fresh waters of El Salvador belong to the class Pisces 
(fishes) and to the superorder Teleostei (the bony fishes), which possess a bony 
skeleton, a well-developed skull, a single gill opening on each side, at least two 
nostrils that are not median, and well-developed fins. 
KEY TO THE FAMILIES OF FISHES OCCURRING IN THE FRESH WATERS OF EL SALVADOR ^ 
a. Scales wanting, body mostly covered witli smooth skin; mouth and nostrils with several pairs 
of barbels or whiskers. 
h. Nostrils close together, neither with a Vjarbel; palatine teeth present Ariidas, p. 248. 
bb. Nostrils remote from each other, the posterior one without a barbel; teeth wanting on 
palatines Pimelodidx, p. 251. 
aa. Body scaled; no barbels about the nostrils or mouth, 
c. Fins without spines. 
d. Adipose fin present; head naked; lateral line present Characinidx, p. 244. 
dd. Adipose fin wanting; head partly scaled; lateral line wanting. 
e. Eye divided into an upper and lower portion by a dark-colored membrane in the 
cornea; anal fin in the male modified into a thick scaly conical copulatory organ 
with an orifice at its extremity Anablepidx, p. 261. 
ee. Eye normal, not as above; anal fin in the male normal or produced, but not forming 
a conical organ with an orifice. 
/. Anal fin modified, the anterior rays more or less produced, forming an intromittent 
organ, but not enveloped in skin and not hollow as in Anableps^-Pcecilvidse, p. 254. 
//. Anal fin normal in both sexes Cyprinodontidse, p. 253. 
cc. Fins with spines. 
g. Body elongate, not very deep; dorsal fins 2, separate. 
h. Ventral fins abdominal; lateral line usually absent, never complete. 
i. First dorsal with 3 to 9 flexible spines; anal fin with a single weak 
spine Atherinidw, p. 263. 
ii. First dorsal with 4 rather strong stiff spines; anal with 3 strong spines 
(sometimes 2 in very young) Mugilidx, p. 265. 
hh. Ventral fins thoracic. 
j. Lateral line complete, continued to end of caudal fin; anal with 3 spines, 
the second very strong; caudal fin forked Centropo7nid3s, p. 268. 
jj. Lateral line wanting; anal fin with a single weak spine; caudal fin 
rounded Eleotridse, p. 281. 
gg. Body deep, compressed; lateral line interrupted under base of dorsal, reappear- 
ing lower down on side; dorsal fin single, composed of spines and rays 
Cichlidx, p. 272. 
2 This key is intended to identify only the species of these families which occur in El Salvador, as some of the characters men- 
tioned are not true of the families as a whole. 
243 
