THE FISHES OF PORTO RICO. 
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a. Intestinal canal comparatively short, little convoluted; teeth little movable; bones of the dentary firmly con- 
nected; lower jaw strong and usually projecting beyond upper; species chiefly carnivorous. 
b. Anal fin of male similar to that of female and not modified into an intromittent organ. Species oviparous. 
c. Teeth all pointed, none of them compressed or bicuspid or tricuspid. 
Fundulin,®: 
d. Teeth in vllliform bands or at least in more than one series. 
e. Air-bladder well developed (in all species examined); no caudal ocellus. 
/. Gill-openings not restricted above, the opercular angle free from shoulder-girdle; body oblong; dorsal various in 
size and insertion Fundulus, 31 
ff. Gill-openings restricted, the opercle from upper root of pectoral upward being adnate to shoulder-girdle, body 
short and deep Adinia 
ee. Air-bladder wanting; a black ocellus at root of caudal, at least in males Rivuliis 
dd. Teeth arranged in a single series; dorsal inserted in advance of anal; mouth oblique. 
g. Dorsal and anal fins short, each of 9 to 13 rays Lucania 
gg. Dorsal and anal fins very long, each of more than 20 rays Girardinichthys 
Cyprinodontin/E: 
cc. Teeth incisor-like, notched, bicuspid or tricuspid. 
h. Ventral fins well developed (occasionally lost through atrophy); gill-openings restricted; opercle adnate above to 
the shoulder-girdle. 
i. Incisors bicuspid, with a band of villiform teeth behind them; body rather deep, vertical fins moderately 
developed Characodon 
ii. Incisors tricuspid, in one row, with no villiform teeth behind them; body short and deep, compressed. 
j. Dorsal fin- short, of 10 to 12 rays, first ray slender and rudimentary Cyprinodon 
jj. Dorsal fin very long, of 16 to 18 rays, first ray developed as a stout, grooved spine Jordanella 
bb. Anal fin in the males placed well forward and modified into a sword-shaped intromittent organ teeth all pointed, 
arranged in bands. Species viviparous or ovoviviparous, the young of large size at birth. 
GAMBUSUNi®: 
k. Eye normal, pupil not divided by a partition; dorsal inserted more or less behind front of anal. 
l. Jaws not produced into a beak, lower jaw prominent, longer than upper; male fish much smaller than female. 
m. Dorsal fin long, of 14 to 16 rays; anal short Pseudoxiphophorus 
mm. Dorsal fin short, of 6 to 10 rays; anal short Gambusia 
U. Jaws produced into a moderate beak, much as in Labidesthes; dorsal and anal short Belonesox 
Anablepin.®: 
- kk. Eye divided into two portions by a horizontal cross partition; vertical fins short; body elongate Anableps 
aa. Intestinal canal elongate, with numerous convolutions; dentary bones loosely joined; teeth movable; species 
chiefly mud-eating. 
Goodeina:: 
n. Teeth incisor-like, all tricuspid, in one series, with a series of villiform teeth behind them; sexual characters unknown, 
the sexes probably alike; lower jaw projecting. 
o. Fins small; scales large; form oblong Goodea 
Pceciliina:: 
nn. Teeth all pointed; anal fin in male advanced and modified into an intromittent organ; lower jaw short and weak. 
Species ovoviviparous. 
p. Teeth in a single series; dorsal and anal both short; scales large. 
q. Dorsal fin inserted in advance of anal Platypcecilus 
qq. Dorsal fin inserted more or less behind front of anal Heterandria 
pp. Teeth in more than one series. 
r. Dorsal inserted more or less behind anal; both fins very small Lebistes 
rr. Dorsal inserted over or in advance of anal, its rays much elevated in male. 
s. Dorsal fin short, of fewer than 12 rays. 
t. Teeth of inner series in both jaws trifid Acropcecilia 
It. Teeth of inner series in both jaws entire Pcecilia, 32 
ss. Dorsal fin long, of 12 to 16 rays. 
u. Caudal fin normal, alike in both sexes, or with the lower angle merely sharp in the male Mollienisia 
uu. Caudal fin in males with its lower lobe much produced and sword-shaped, in adult as long as the rest of the 
body Xiphophorus 
Genus 31. FUNDULUS Lacepede. Killi-fishes. 
Body rather elongate, little elevated, compressed behind. Mouth moderate, lower jaw projecting. 
Jaws each with two or -more series of pointed teeth, usually forming a narrow band. Bones of the 
mandible firmly united. Scales moderate. Hill-opening not restricted above, opercle with its margin 
not adnate to shoulder-girdle. Preopercle, preorbital, and mandible with mucous pores. Dorsal and 
anal fins similar, small or rather large, dorsal inserted either in front of, above, or behind front of 
anal; ventrals well developed. Air-bladder present. Sexes differing in color, size, and development 
