GERRES. 37 
Fam. 9. LIOGNATHIDA. 
The Liognathide comprise the four genera Gerres, Pentaprion, Liognathus, and 
Gazza. The three last-named appear to be exclusively marine and are confined to the 
tropical Indo-Pacific. Gerres is found in all tropical seas, and most of the species 
appear to freely enter fresh water. 
1. GERRES, Cuv., 1829. 
Gerres, Giinth. Cat. Fish. iv. p. 252 (1862). 
Eucinostomus, Ulema, Xystema, and Gerres, Jord. & Everm. Bull. U.S. Nat. Mus. xlvii. 1898, 
pp. 1867, 1371, 1372, and 1373. 
Body compressed; scales large or moderate, cycloid or finely ctenoid. Lateral line complete. Mouth 
moderate, very protractile ; maxillary exposed; jaws equal anteriorly ; bands of small villiform teeth in 
Jaws ; palate toothless. Préorbital and preoperculum entire or finely serrated. A single dorsal with 
IX 10 rays, with a scaly sheath at the base ; second or third dorsal spine the longest ; anal with IT-III 
7-9 rays; caudal forked; pectoral asymmetrical, pointed ; ventrals a little behind the base of pectorals, 
with I 5 rays ; a scaly process at base of spine of each ventral fin. 
Hab. Tropical seas, entering rivers. 
The American species of Gerres number seventeen, and although only a small 
proportion of these have been recorded from rivers or lakes in Mexico and Central 
America, we may feel quite sure that most of them are to be met with there. It is 
rather a difficult matter to know how to deal with such a group in a work on fresh- 
water fishes, but I have thought it more useful to prepare a synopsis of all the 
American species, based on an examination of the available material, rather than to 
give descriptions of the few definitely known to occur in the fresh waters of Mexico 
and Central America. 
Synopsis of the Species. 
I. Preeoperculum entire. 
A. Anal III 7. 
1. Second anal spine 4} the length of head ; second dorsal spine a little longer than 
third; depth of body 23-21 in the length. 
5 or 53 scales between lateral line and middle of dorsal fin . . . . . . . UL. cinereus. 
4 scales between lateral line and middle of dorsal fin . . . . . . . . . 2. simillimus. 
2. Second anal spine from less than } to slightly more than } the length of head ; second 
dorsal spine a little shorter than third. 
a, Premaxillary processes (measured from anterior edge of upper jaw to their posterior 
extremities) more than 4 the length of head. 
Snout a little shorter than eye; maxillary extending to below anterior margin 
of eye; depth of body 2}-22 in the length; 7 gill-rakers on the lower 
partofanteriorarch . . 2... kk gula. 
