170 



LOWER VERTEBRATES. 



These are greenish in color, and banded or reticulated, rather than spotted, and, in all, 

 the opercles as well as the cheeks are fully covered with scales. One of these {Esox. 

 reticularis) is the common pickerel of the Eastern States, which reaches a respectable 

 size, and is excellent as food. The others (Esox americamcs, Esox vermiculatus) 

 seldom exceed a foot in length, and have no economic importance. 



Closely allied to the Esocidae is the small family of the mud-minnows, or.TJMBKiD^, 



which technically differ from the pike, 

 chiefly in the smaller mouth and weak 

 dentition. The two known species reach 

 but a small size, and their distribution is 

 somewhat anomalous, indicating perhaps a 

 former wider range. 



The species are sluggish, carnivorous 

 fishes, living in weeds or mud at the bot- 

 toms of clear streams or ponds in rather cold regions. They are very tenacious of life, 

 but do not live long in warm or turbid waters. 



Of the known species, the Hundsfisch ( Umh-a crameri) is found in Austria. Its 

 near relative, the mud minnow ( Uhibra limi) abounds in the streams and swamps 

 of the northern states. It often lives for a long time imbedded in the mud of prairie 

 sloughs and bog-holes, where it has sometimes been ploughed up alive. 



The large family of Cypeinodoxtid^ or killifishes, is distinguished among the 

 Haplomi by the structure of its mouth. The short upper jaw is extremely protractile. 



Fig. 103, — Umbra limi, iiiud niimio-\v. 



Fig. 104. — Anabkps tetrophthalmus. 



and its margin is formed by the premaxillaries alone. The teeth are small, and of 

 various forms. The scales are large and cover the top and sides of the head. The 

 stomach is without pyloric cceca, and the intestines are long or short according to the 

 food of the fish. 



