BIOLOGIA CENTRALI-AMERICANA. 
ZOOLOGIA. 
Class PISCES. 
Sub-class I, TELEOSTOMI. 
Order I. TELEOSTEI. 
Sub-order I. ACANTHOPTERYGII. 
It has been found convenient to commence an account of the Fresh-water Fishes of 
Mexico and Central America with the Acanthopterygii, which may be recognized by 
the thoracic or jugular position of the ventral fins, the pelvic bones being directly 
attached to the clavicles. 
The Acanthopterygian fresh-water fishes of Mexico and Central America may be 
referred to their families by means of the following key :— 
I. Head asymmetrical, with the two eyes on one side; fins without spines. 1. PLevRoNECTIDA. 
II. Head symmetrical. 
A. Gill-openings restricted, the gill-membranes attached to the isthmus. 
Ventral fins widely separated, jugular; dorsal and anal fins short, 
without spinous rays . . . . . 1 ww we eee GoBrEsocipé. 
Ventral fins not widely separated, thoracic; two dorsals or the dorsal 
fnlong . . . . . . ew. ee ee eee 8. GoBrr ee. 
B. Gill-membranes free from the isthmus. 
1. Anal fin with 8 spines, 2 of which are detached from the rest of the 
fine 2. ee ee ee A CaRANGID a. 
2. Anal fin not preceded by free spines. 
a. A single nostril on each side. Dorsal with XIV-XIX 7-15 * rays. 
Anal with III-XII 6-l2 rays . 2 2... ww. OS Cronin. 
* The Roman numerals indicate the number of spines, the Arabic figures the number of articulated rays. 
BIOL. CENTR.-AMER., Pisces, October 1906. B 
