194 The Scyphophori, Haplomi, and Xenomi 
mud-minnows are small, sluggish, carnivorous fishes living in 
the mud at the bottom of cold, clear streams and ponds. They 
are extremely tenacious of life, though soon suffocated in warm 
waters. The barred mud-minnow of the prairies of the middle 
West (Umbra limz) often remains in dried sloughs and bog- 
holes, and has been sometimes plowed up alive. Umbra pygmea, 
a striped species, is found in the Eastern States and Umbra 
cramert in bogs and brooks along the Danube. This wide break 
in distribution seems to indicate a former wide extension of 
the range of Umbride, perhaps coextensive with Esox. Fossil 
Umbrideé are, however, not yet recognized. 
The Killifishes—Most of the recent Haplomi belong to the 
family of Peciliide (killifishes, or Cyprinodonts). In this 
group the small mouth is extremely protractile, its margin 
formed by the premaxillaries alone much as in the spiny- 
rayed fishes. The teeth are small and of various forms accord- 
ing to the food. In most of the herbivorous forms they are 
incisor-like, serrate, and loosely inserted in the lips. In the 
species that eat insects or worms they are more firmly fixed. 
The head is scaly, the stomach without ceca, and the intes- 
tines are long in the plant-eating species and short in the 
others. There are nearly 200 species, very abundant from 
New England and California southward to Argentina, and 
in Asia and Africa also. In regions where rice is produced, 
they swarm in the rice swamps and ditches. Some of them 
enter the sea, but none of them go far from shore. Some 
are brilliantly colored, and in many species the males are quite 
unlike the females, being smaller and more showy. The largest 
species (Fundulus, Anableps) rarely reach the length of a foot, 
while Heterandria formosa, a diminutive inhabitant of the 
Florida rivers, scarcely reaches an inch. Some species are 
oviparous, but in most of the herbivorous forms, and some of 
the others, the eggs are hatched within the body, and the anal 
in the male is modified into a long sword-shaped intromittent 
organ, placed farther forward than the anal in the female. 
The young when born closely resemble the parent. Most of 
the insectivorous species swim at the surface, moving slowly 
with the eyes partly out of water. This habit in the genus 
Anableps (four-eyed fish, or Cuatro ojos) is associated with an 
