448 TEXTBOOK OF ZOOLOGY 



scales. There are three species in our western streams and in the 

 Great Lakes. Hiodon tergisus is the form found in the Mississippi 

 Valley. 



Family Albulidae. — Ladyfishes. A small group of a few species 

 found in warm marine waters. 



Family Dussumuriidae. — Round Herrings. This is a scarce, small, 

 bluish fish, with a rounded belly outline. 



Family Clupeidae. — Herrings. This family includes a large num- 

 ber of species, and it is thought that there are more individuals in 

 this group than in any other. They are found in most seas, and 

 many species enter fresh water to spawn, but there are very few 

 fresh-water species. The family includes many valuable food fishes 

 of which Clupea harengus is the most important. 



Family Dorosomidae. — Gizzard Shads. This is an abundant, widely 

 distributed, prolific, but almost inedible, group of fish. The body 

 is quite flat from side to side, and the edges are thin. There is a 

 filament extending from last ray of the dorsal fin. 



Family Engraulidae. — Anchovies. These fish have elongated, small, 

 compressed bodies. They are abundant in warm seas and swim in 

 large schools. Anchoviella (Anchovia) mitcMlli is one of the most 

 common American forms. 



Family Coregonidae. — Whitefishes. There are about twenty fresh- 

 water lake species. This is an important commercial fish. Ciscos 

 are included in this group also. 



Family Salmonidae. — Salmon and Trout. This is a group of 

 elongate, moderately compressed, large-mouthed fish with fine scales, 

 a lateral line and, internally, a large number of pyloric caeca. They 

 are principally northern and abound in clear waters north of lati- 

 tude 40°. They are noted as game and food fish. 



Family Thymallidae. — Graylings. These fish resemble the previ- 

 ous group in many ways, but they have a large dorsal fin. The 

 Michigan Grayling, Thymallus tricolor, is a typical species. It is 

 a northern fish. 



Family Osmeridae. — Smelts. These differ from Salmonidae chiefly 

 in the presence of a blind saclike stomach. The esophagus and 

 pylorus join close together. 



