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 limi) often remains in dried sloughs and bog- 

 holes, and has been sometimes plowed up alive. Umbra pygmaa, 

 a striped species, is found in the Eastern States and Umbra 

 crameri in bogs and brooks along the Danube. This wide break 

 in distribution seems to indicate a former wide extension of 

 the range of Umbrida>, perhaps coextensive with Esox. Fossil 

 Umbrida are, however, not yet recognized. 



The Killifishes. Most of the recent Haplomi belong to the 

 family of Pceciliidcz (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 caeca, 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 



