380 Series Ostariophysi 
four orders: Heterognathi, Eventognathi (Plectospondyli), Nema- 
tognatht, and Gymnonott. 
The Heterognathi.—Of these the order of Heterognathi seems 
to be the most primitive, but in some ways the most highly de- 
veloped, showing fewer traits of degeneration than any of the 
others. The presence of the adipose fin in this group and in 
the catfishes seems to indicate some sort of real affinity with 
the salmon-like forms, although there has been great change in 
other regards. 
The order Heterognatht, or Characini (érepos, different; yva- 
fos, jaw), contains those Ostariophysi which retain the meso- 
coracoid and are not eel-like, and which have the lower pharyn- 
geals developed as in ordinary fishes. In most cases an adipose 
fin is present and there are strong teeth in the jaws. There are 
no pseudobranchie, and, as in the Cyprinide, usually but three 
branchiostegals. The Characide constitute the majority of the 
fresh-water fishes in those regions which have neither Cyprinide 
nor Salmonide. Nearly four hundred species are known from 
the rivers of South America and Africa. A single species, 
Tetragonopterus argentatus, extends its range northward to the 
Rio Grande in Texas. None are found in Asia, Europe, or, with 
this single exception, in the United States. Most of them are 
small fishes with deep bodies and very sharp, serrated, incisor- 
like teeth. Some are as innocuous as minnows, which they very 
much resemble, but others are extremely voracious.and destruc- 
tive in the highest degree. Of the caribe, belonging to the 
genus Serrasalmo, known by its. serrated belly, Dr. Gunther 
observes : 
“Their voracity, fearlessness and number render them a 
perfect pest in many rivers of tropical America. In all the 
teeth are strong, short, sharp, sometimes lobed incisors, arranged 
in one or more series; by means of them they cut off a mouth- 
ful of flesh as with a pair of scissors; and any animal falling 
into the water where these fish abound is immediately attacked 
and cut to pieces in an incredibly short time. They assail 
persons entering the water, inflicting dangerous wounds before 
the victims are able to make their escape. In some localities 
it is scarcely possible to catch fishes with the hook and line, as 
the fish hooked is immediately attacked by the ‘caribe’ (as 
