THE FISHES OF I'ORTO RIOO. 
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Family XLV1I. GERRID£. The Mojarras. 
Body oblong or elevated, compressed, covered with large, smooth scales; lateral line continuous, 
concurrent with back; mouth moderate, extremely protractile, descending when protruded, spines of 
premaxillary extending to above eye, closing a deep groove in top of head; maxillary without 
supplemental bone, not slipping under very narrow preorbital, its surface silvery, like rest of head; 
base of mandible scaly, a slit between it and preorbital to permit its free motion; both jaws with slender, 
villiform teeth; no incisors, canines, nor molars; no teeth on vomer or palatines; preopercle entire or 
serrate; sides of head scaly; nostrils double, round; pseudobranchise concealed ; gill rakers short, broad ; 
gill-membranes separate, free from isthmus; dorsal fin single, continuous or deeply notched, spinous 
ami soft portions about equally developed, with a scaly sheath along base; dorsal spines usually 9 or 
10; anal usually with 3 spines; soft portion of fin similar to soft dorsal but shorter; ventral fins 
thoracic, i, 5, rather close together, slightly behind pectorals; branch iostegals 6; lower pharyngeal 
bones close together, often appearing to be united, teeth blunt; air-bladder present; pyloric caeca 
rudimentary; vertebrae 10 -j- 14 = 24. 
The Gerridx comprise 6 or 8 genera and about 40 species. Four American genera are now recog- 
nized, and each is represented in Porto Rican waters by one or more species. They are carnivorous 
fishes, of moderate or small size, inhabiting the tropical seas, differing considerably in form and in 
development of spines; the intergradations are, however, very perfect, so that but for the osteological 
peculiarities of certain species all might be placed in one genus. Oviparous. The larger species of this 
family are used as food, though they do not seem to be highly esteemed anywhere. In Indian River, 
Florida, they are rarely used, but about Porto Rico they are in better demand. 
a. Dorsal fin continuous, deeply notched. 
b. Second interhsemal spine singularly developed, as a hollow cylinder, comparatively short and much expanded, 
posterior end of air-bladder entering its cavity; preopercle and preorbital entire, anal spines 3, second not 
much enlarged Eucinostomus, 89 
bb. Second interhsemal spine normally developed, not hollow, air-bladder not entering it. 
c. Second interhsemal spine very short, bluntish ; anal spines 2, both small ; preopercle and preorbital 
entire Ul,ema,90 
cc. Second interhsemal spine long, spear-shaped; anal spines 2 or 3, second enlarged 
d. Preopercle entire; second anal spine moderate X ysttema, 91 
dd. Preopercle serrate; second anal spine much enlarged Gerres,92 
Genus 89. EUCINOSTOMUS Baird & Girard. Mojarritas 
Interhsemal of second anal spine greatly modified, expanded into a hollow cylinder, into which 
posterior end of air-bladder enters. Preopercle and preorbital entire; body comparatively elongate, 
subelliptical in form; anal spines 3; second anal spine and fourth dorsal spine not greatly enlarged. 
Species numerous, in warm seas, remarkable for the peculiar structure of the second interhsemal, 
which is formed somewhat as in Calamus, but much more modified than in that genus. 
a. Premaxillary groove wholly naked, linear or semioval, sometimes constricted at base, but never scaled, anal 
rays III, 7. 
b. Eye very large, its diameter much greater than length of snout, 2.66 in length of head. . Exposed portion of maxil- 
lary small, triangular; premaxillary groove linear dowi 
bb. Eye moderate, usually more than 3 in head, its diameter about equal to length of snout Exposed portion of 
maxillary triangular in front, oblong behind. 
c. Body elongate, back little elevated; greatest depth 3.25 to 3.5 in length pseudogula, 158 
cc. Body more compressed, deeper, back more elevated; greatest depth 2.66 in length. 
d. Snout blunt; eye large, scarcely 3 in head; second anal spine large, 2.66 to 3.3 in head, premaxillary groove 
linear harengulus, 159 
aa. Premaxillary groove scaled in front, scales leaving a naked pit behind Depth 2.4 in length; head 3 to 3.2 in 
length of body. Second anal spine about 3.5 in head. grata, 160 
158. Eucinostomus pseudogula Poey. Mojarra. 
Head 3.2; depth 3.3; eye 3; snout 3.25; maxillary 3.3; mandible 2; interorbital 3.6; scales 5-49-9; 
D. ix, 10; A. ni, 7. Body compressed, very slender, back very little elevated, the curve a gentle, regular 
one from nape to caudal peduncle; mouth moderate, nearly horizontal, maxillary reaching anterior 
edge of pupil, exposed portion triangular; preorbital and preopercle entire, eye large; premaxillary 
groove rather narrow and without scales; snout rather long and pointed. Fins moderate; dorsal spines 
