FISHES FROM CENTRAL AND NORTHERN MEXICO. 
G5 
RIO BLANCO AT ORIZABA. 
Orizaba is a city iu tbe central part of tbe State of Yera Cruz, on the Mexico and 
Vera Cruz Eaihvay, about 175 miles southeast of the City of Mexico and 65 miles north- 
west of Vera Cruz. It has iiossibly 10,000 inhabitants, and is situated about 4,000 feet 
above sea level, in the foothills of Mount Orizaba, or Citlaltepetl, the highest mountain 
in Mexico. It is located on a branch of the Eio Blanco, which flows nearly due east to 
the Gulf of Mexico. This branch of the river rises a short distance north of the town 
of Orizaba, in large deep springs, which, during the Avet season, spread over seA^'eral 
acres of ground. The stream flows a distance of about 120 kilometers before reaching 
the gulf, and in this distance falls more than 4,000 feet. It passes for the most part 
over a series of rapids at an average rate of iiossibly G miles an hour, in many iilaces 
making perpendicular descents, and iu one instance falling more than 100 feet in a 
single leap. That the fishes found in this locality have inhabited these waters for a 
very long time is evident, since it would be impossible for them to ascend from the 
lower lands. Only a single species was taken at this place, and it was very abundant. 
It Avas taken from the mill race about the water wheels, and in the bath house, Wher- 
6Amr a nook of quiet water occurred this little fish could be seen in great numbers, 
SAvimming near the surface of the water. A Spanish boy who assisted in capturing 
the specimens insisted that much larger ones were sometimes found, and Avere fre- 
quently taken during times of Ioat Avater ; and it is due to his ingenuity that the largest 
and finest specimens that I brought away Avere obtained. 
1. Pseudoxiphopliorus bimaculatus (Haeckel). {Xiphophorus himaculaius H.iec'kel, Sitzgsber. Akad. 
Wiss. Wien, 1848, p. 196.) 
The geuus rseudoxipliopliorm differs from Gamhusia chielly iu the long dorsal, and this 
characteristic is of doubtful value since the imiuber of rays range from 12 to 15, those of 
Gamhusia rangiug from 7 to 10. Haeckel describes two species of rsemloxiphopliorus from 
the Orizaba region. These he distinguishes by the form of the anal process, hooked in 
bimacu.Iatus and straight iu reticulaius. Bbnaculatus has dorsal 14, anal 10. llcticulatus has 
dorsal 16 and anal 10. I find both forms iu my collection, but doubt the Amlue of the dis- 
tinctions, as it is not unlikely that they represent simply extremes of variations. P. hhnac- 
vlatus (the Anriety with the longer anal) is by far the more abundant. The form of the 
anal process seems to be of slight importance. The length, howeA'er, is fpiite Aurriable, luit 
Avhether or not the end is curA'ed seems rather to dexiend upon the length. The longer the 
organ the more liable it is to be curved. In most of my specimens, however, the organ is 
nearly straight. 
The general color in P. himaculatns is uniform olive-broAvn with the posterior jiart of 
each scale marked with a crescent-shaped spot ; a large steel blue spot on the opercle just 
behind the eye; cheeks, lower jrart of the opercle, and breast from the jAectorals doAvn, 
and anterior part of the belly, orange; humeral scale black, but not enlarged; a large dark 
ocellus, about the size of the eye, oil the upper iiosterior margin of the caudal peduncle. 
Dorsal flu with a row of dark spots on membrane, at about midivay of rays; also a second 
row of spots near base of fin. The anal flu is marked similarly, except the anterior part is 
plain, giving it the appearance of a dark spot on anal ; pectoral, ventral, and caudal fins 
almost plain. Body moderately elongated, slightly but regularly arched above ; head A'ery 
broad and low, so that the upper margin of the orbit is nearly on a ievel wilh top of head 
between the eyes ; belly much decurved ; line of curvature quite regular from the upper 
margin of the lower lip to origin of veutrals; upper margin of lower lip, Avhen mouth is 
closed, on a level with top of pupil; also on a level with the second row of scales from 
dorsal. Eye medium, orbit circular, the diameter of which is about the length of snout, 
34 in head, or 2j: in iuterorbital area. Scales large, deeper than Ions; 12 rows Avith from 
29 to 31 scales iu length of body ; 13 or 14 before dorsal. 
F. C. B. 189i 5 
