HAG-FISHES. 113 



six or seven on each side. There is a single nasal aperture. The 

 mouth is anterior and suctorialj surrounded by a circular or sub- 

 circular lip. 



This Subclass comprises the Lampreys [Petromyzon] and Hag- 

 fish {Myxine). The former are found in the rivers and on the 

 coasts of the temperate regions of the northern and southern 

 hemispheres, Their habits are but incompletely known, but so 

 much is certain that at least some of them ascend rivers periodically 

 for the purpose of spawning, and that the young pass several years 

 in rivers whilst they undergo a metamorphosis. In the larvae 

 the mouth is toothless, and surrounded by an imperfect lip. The 

 Lampreys feed on other fishes, to which they suck themselves fast, 

 scraping off the flesh with their teeth. Whilst thus engaged they 

 are carried about by their victim. The British species are the Sea- 

 Lamprey {Petromyzon marinus), exceeding a length of three feet, 

 and not uncommon on the European and North-American coasts ; 

 the River- Lam prey or Lampern {P. fluviatilis), ascending iu large 

 numbers the rivers of Europe, North America, and Japan, and 

 scarcely attaining a length of two feet ; the " Pride " or " Sand- 

 piper" or "Small Lampern" [P. branchialis) , scarcely 12 inches 

 long, the larva of which has long been known under the name of 

 Ammoccstes. The Hag-fishes, or Myxine (fig. 100), are marine fishes 



Fig. 100. 



Hag (Myxine). (From the German Ocean.) 

 g. Gill-opening. 



most plentiful in the higher latitudes of the temperate zones of the 

 northern and southern hemispheres ; some descend to a depth of 

 345 fathoms. They are frequently found buried in the abdominal 

 cavity of other fishes, especially Gadoids, into which they penetrate 

 to feed on their flesh. When caught, they secrete a thick glutinous 

 slime in incredible quantities, and are therefore considered by 

 fishermen a great nuisance, seriously interfering with the fishing 

 in localities where they aboand. 



