XENATHERINA.—MUGILIDA. 60 
of small scales. Dorsal III-V, I 8-9; origin of spinous dorsal above or a little behind that of the anal. 
Anal I 19-21. Pectoral asymmetrical, pointed, # the length of head, extending to above the middle of 
ventrals, Caudal forked. Caudal peduncle twice as long as deep. 
Hab. Mexico, Rio Papaloapam : 
Refugio !, El Hule}. 
Here described from five specimens, measuring up to 55 mm. in total length, from 
Refugio (Meek). 
Fam, 2. MUGILIDA. 
The Mugilide are closely related to the Atherinide and have the same wide 
distribution. Most of the species of Mugil and allied genera with ciliiform teeth are 
marine, but freely enter fresh water. Agonostomus and Jotwrus comprise tropical 
fresh-water fishes, especially abundant in mountain-streams. 
The Mexican and Central-American Mugilidee have the following features in 
common :—Body elongate, more or less compressed, covered with rather large scales, 
which extend on to the upper surface of the head. Lateral line usually absent, never 
complete. Two well-separated dorsal fins, the first formed of 4 rather strong spines, 
the second of a spine and 7 to 10 articulated rays. Anal with 2 or 3 spines and 
7 to 11 articulated rays. Pectorals placed high; ventrals abdominal, each with one 
spine and 5 branched rays. Caudal forked. Preemaxillaries protractile ; jaws with 
teeth, which may be either well-developed or vestigial; palate with or without teeth. 
Coloration silvery, the back greenish or olivaceous; sometimes dark longitudinal 
stripes along the series of scales. | | 
Synopsis of the Mexican and Central-American Genera. 
J. Bands of small fixed teeth in the jaws and on the palate. 
Teeth in the jaws pointed . . . . - . ee ee ehhh he 6. AGONOSTOMUS. 
Teeth in the jaws incisor-like, with serrated edges wee ew ee ee 6 JSOTURUS. 
II. Teeth in the jaws small, in one or more series ; palate toothless. 
A. Teeth ciliiform, in one or a few series; lips not very thick; rami of lower jaw meeting at 
an angle which is not very acute. 
Three anal spines. . . 2. ee ee te ee ee ee 8, Moet. 
Two analspines . . . 2 2 ee ee ee eee ee ee 4, QUERIMANA. 
B. Teeth in several oblique series ; lips thick; rami of lower jaw 
meeting at anacute angle . . . . 1. 2 « «© + + + «© « « 5, CHHNOMUGIL. 
I have given full descriptions of the Mexican and Central-American species of the 
genera Agonostomus and Joturus, which appear to be true fresh-water fishes, and for 
purposes of comparison I have included in my account of the former genus two species, 
A. percoides and A. microps, which are at present known only from specimens in the 
BIOL. CENTR.-AMER., Pisces, May 1907. K 
