FISHES FROM THE RIVERS OF MEXICO. 
127 
Color in alcohol, light yellowish-olive; 9 short and narrow dark vertical hands on median part 
of body; the iirst above base of pectoral; the ninth at base of caudal; scales on dorsal region of 
body edged with black dots; upper part of head dark; upper half of orbit black; opercles silvery; 
dorsal fin with a little dusky; other fins without dark color. 
Charaoodon encaustus somewhat resembles C. eiseiii in appearance. It differs in having more rays 
in the dorsal and anal fins, smaller scales, a more compressed body, and less dark color on the body. 
One female specimen only was collected. 
21 Cyprinodon elegans Baird & Girard. 
Three small female specimens of Cyprinodon from lagoons near Tampico are, with some doubt, 
referred to the species elegans. 
22 . Gambusia affinis Baird & Girard. 
A number of males and females of Gambusia affinis were collected in lagoons near Tampico, and 
especially in small pools left by high water. 
XENENDUM Jordan & Snyder, new genus. 
Type, Xenendum caliente, new species. 
Body deep, not much compressed. Males and females of about the same size. Eye normal. 
Mouth vertical, lower jaw projecting. Teeth loosely attached, in 2 series ; first series flat, bicuspid, in 
2 or 3 rows on each jaw ; second series minute, in villiform bauds, sometimes absent. Gill-openings 
not restricted, extending above the pectoral fin a distance equal to diameter of pupil. Alimentary 
canal long, with many convolutions. Air-bladder present, large. Scales large. No lateral line. 
Dorsal and anal inserted posteriorly, the one directly over the other, their bases short; anal very 
Fig. 8 . — Xenendum caliente Jordan & Snyder, new genus and species. Type, 
slightly modified in male, first rays shorter; edge of fin double convex — the notch being between the 
smaller and larger groups of rays. Ventral fins present. Caudal rounded, and not modified in male. 
Xenendum differs notably from Clmracodon in having the bicuspid teeth loosely attached and in 
more than one series. Characodon has the bicuspid teeth firmly attached aud in a single series. The 
actual affinities of Xenendum are with the genus Goodea, and it belongs to the subfamily Goodeina;, 
which has the general characters of the Pceciliince, but with bifurcate or trifurcate teeth and no great 
differences between the sexes. Characodon luitpoldi Steindachner seems to be a species of Xenendum. 
23. Xenendum caliente Jordan & Snyder, new species. Fig. 8. 
One male specimen, type No. 6147, L. S. Jr. Univ. Mus., from Rio Verde near Aguas Calientes, 
Mexico. Collected by .1. O. Snyder, January 9, 1899. 
Head 3.75 in length; depth 2.60; depth of caudal peduncle 5.66; eye 4 in head; snout 3.20; 
interorbital space 2; height of dorsal 5.66 in length; anal 6.75; length of pectoral 5; ventral 7.66; 
caudal 5. D. 13. A. 14. Scales in lateral series 36; transverse series counting upward and forward 
from origin of anal 14; on caudal peduncle 9. 
Body large and thickset, deepest part at tip of pectoral ; width contained 4f times in length; 
head pointed; interorbital space broad; slightly convex; length of snout about equal to diameter of 
orbit; mouth vertical, its width equal to length of snout; maxillary very protractile. Teeth loosely 
attached in 2 series, tffose of first series larger, flat, and notched, in 2 rows on upper jaw, 3 rows on 
lower, the individual teeth of each row alternating in position with those of the next; those of second 
series very minute in a villiform band. Gill-openings not restricted, extending above the pectoral a 
distance equal to diameter of pupil. Gillrakers long, slender, and close together, 40 on first arch. 
