Fig. 157.—Top-minnow, Zygonectes notatus (Rafinesque). Eureka Springs, Ark.
Fig. 158.—Death Valley Fish, Empetrichthys merriami Gilbert. Amargosa Desert, Cal. Family Pœciliidæ. (After Gilbert.)
Fig. 159.—Sword-tail Minnow, male, Xiphophorus helleri Heckel. The anal fin modified as an intromittent organ. Vera Cruz.
Of the many genera of Pœciliidæ, top-minnows, and killifishes we may mention the following: Cyprinodon is made up of chubby little fishes of eastern America with tricuspid, incisor teeth, oviparous and omnivorous. Very similar to these but smaller are the species of Lebias in southern Europe. Jordanella floridæ of the Florida everglades is similar, but with the dorsal fin long and its first ray enlarged and spine-like. It strongly resembles a young sunfish. Most of the larger forms belong to Fundulus, a genus widely distributed from Maine to Guatemala and north to Kansas and southern California. Fundulus majalis, the Mayfish of the Atlantic Coast, is the largest of the genus. Fundulus heteroclitus, the killifish, the most abundant. Fundulus diaphanus inhabits sea and lake indiscriminately. Fundulus stellifer of the Alabama is beautifully colored, as is Fundulus zebrinus of the Rio Grande. The genus Zygonectes includes dwarf species similar to Fundulus, and Adinia includes those with short, deep body. Goodea atripinnis with tricuspid teeth lives in warm springs in Mexico, and several species of Goodea, Gambusia, Pœcilia, and other genera inhabit hot springs of Mexico, Central America, and Africa. The genus Gambusia, the top-minnows, includes numerous species with dwarf males having the anal modified. Gambusia affinis abounds in all kinds of sluggish water in the southern lowlands, gutters and even sewers included. It brings forth its brood in early spring. Viviparous and herbivorous with modified anal fin are the species of Pœcilia, abundant throughout Mexico and southward to Brazil; Mollienesia very similar, with a banner-like dorsal fin, showily marked, occurs from Louisiana southward, and Xiphophorus, with a sword-shaped lobe on the caudal, abounds in Mexico; Characodon and Goodea (see Fig. 53, Vol. I) in Mexico have notched teeth, and finally, Heterandria contains some of the least of fishes, the handsomely colored males barely half an inch long.
Fig. 160.—Goodea luitpoldi (Steindachner). A viviparous fish from Lake Patzcuaro, Mexico. Family Pœciliidæ. (After Meek.)
In Lake Titicaca in the high Andes is a peculiar genus (Orestias) without ventral fins. Still more peculiar is Empetrichthys merriami of the desert springs of the hot and rainless Death Valley in California, similar to Orestias, but with enormously enlarged pharyngeals and pharyngeal teeth, an adaptation to some unknown purpose. Fossil Cyprinodonts are not rare from the Miocene in southern Europe. The numerous species are allied to Lebias and Cyprinodon, and are referred to Prolebias and Pachylebias. None are American, although two American extinct genera, Gephyrura and Proballostomus, are probably allied to this group.
Amblyopsidæ.—The cavefishes, Amblyopsidæ, are the most remarkable of the haplomous fishes. In this family the vent is placed at the throat. The form is that of the Pœciliidæ, but the mouth is larger and not protractile. The species are viviparous, the young being born at about the length of a quarter of an inch.