350 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



double tooth, situated above the aperture of the mouth, indicates the 

 situation of the upper jaw; a large cartilage, supporting seven or eight 

 great teeth, represents the lower jaw. The tongue also carries three 

 large teeth, deeply serrated upon their edges. 



The structure of the intestine, which, as- in the sharks, is provided 

 with an extensive spiral valve, indicates that these animals are chiefly 

 carnivorous in diet. They are said to feed upon worms, insects, and 

 decaying animal matter. 



Dr. Benecke, of Konigsberg, Germany, and others have found their 

 stomachs full of fish eggs. The structure of the mouth, however, would 

 teach us, even in default of observations upon their customany mode of 

 feeding, that they are semi-parasitic in their habits, attaching them- 

 selves to large fish by suctorial action, and, while attached, tearing the 

 flesh of the fish with their marvelous mincing machine, which is com- 

 posed of the teeth within the circular mouth, while they suck the blood 

 of their victim. They are often found attached to the larger fishes, 

 such as shad, sturgeon, and sharks. 



Captain Atwood states that small lampreys of a bluish color are found 

 attached to various species of fish in Massachusetts Bay, such as cod, 

 haddock, and mackerel. They cling to the side of the fish beueath the 

 pectoral and suck their blood until the flesh of their prey seems as 

 white as paper. 



There can be but little doubt that to the lampreys may be credited 

 an immense destruction of the various food-fishes which enter estuaries 

 and rivers. It is by no means uncommon for fishermen to find them 

 attached to halibut and other large species caught at sea. Lampreys 

 are found far inland, ascending most of the creeks and rivers of Central 

 Europe and of temperate North America far toward their sources. In 

 fact the distances from the sea, at which the so-called sea-lamprey of 

 Europe is constantly found, are so great, when their feeble powers of 

 locomotion are considered, that Dr. Giinther in his essay on the fishes 

 of the Neckar was induced to advance the theory that they are car- 

 ried from the sea to the river sources by the shad, salmon, and other 

 fish to which the lampreys attach themselves. This view is combated 

 by De La Blanchere, who claims that no one has ever seen lampreys 

 attached to salmon. If I am correctly informed, salmon are largely 

 annoyed by lampreys in the United States, but it seems hardly neces- 

 sary at present to accept Gunther's theory in the fullest extent, since 

 the lamprey is apparently not much inferior to the eel in powers of 

 locomotion, and the eel, it is well known, accomplishes long migrations 

 without apparent inconvenience. 



It has been customary among writers upon fishes to class the lam- 

 preys among the migratory fishes, and to describe the migrations of the 

 sea-lampreys as beginning in the spring, when they are supposed to 

 ascend the rivers for the purpose of spawning in their headwaters. 

 This theory seems at present hardly tenable; so little, however, is 



