56 PERCESOCES. 
Sub-order III. PERCESOCES. 
The Fishes of this sub-order differ from the Acanthopterygii in the abdominal 
position of the ventral fins, the pelvic bones not being directly attached to the clavicles. 
In all the American species there are two well-separated dorsal fins, the first of which 
is formed of from 3 to 9 spines, the second of a spine and 7 to 15 articulated rays. 
The anal fin is wholly or partly opposed to the second dorsal and has from 1 to 3 
spines. The ventral fins are inserted well behind the base of the pectorals; each 
consists of a spine and 5 branched rays. The caudal fin is forked. 
Each of the four families is marine and widely distributed. The majority of the 
species are shore-fishes which frequent the mouths of rivers and sometimes ascend 
into fresh water. The Atherinide and Mugilide include a number of permanently 
fluviatile forms. 
Synopsis of the American Families of the Sub-order Percesoces. 
I. Lateral line usually absent, never complete ; pectoral fins placed high. 
Anterior dorsal of 3 to 8 slender spines; a single anal spine; vertebre 
32 to 60 . a 
Anterior dorsal of 3 to 5 pungent spines ; 2 or 3 anal spines; vertebra 
24 to 26 . 
1. ATHERINIDZ. 
2. Mucitipz. 
II. Lateral line present, complete ; pectoral fins placed low. 
Pectoral fin normal . 8. SPHYRENIDZ. 
Pectoral fin with a detached lower portion composed of free filamentous 
rays 4. PoLyNEMID&. 
Fam. 1. ATHERINIDZ. 
The Atherinide occur on the coasts of most tropical and temperate seas; a consi- 
derable number of them enter or permanently inhabit fresh waters. Those found in 
the rivers and lakes of Mexico and Central America have the following features in 
common :—Body elongate, more or less compressed. Lateral line usually absent, 
never complete. ‘Two well-separated dorsal fins, the first formed of 8 to 6 slender 
spines, the second of a short spine and 7 to 13 articulated rays. Anal with one 
spine and 12 to 25 articulated rays. Pectorals placed high ; ventrals abdominal, each 
with one spine and 5 branched rays. Caudal forked. Premaxillaries protractile ; 
jaws with two or more series of conical teeth; palate toothless, or a few teeth on 
the vomer. A silvery lateral longitudinal band or stripe always present. 
