214 THE CARTILAGINOUS FISHES 



larva is termed the Ammoccetes by scientists, but among country 

 people it is popularly known as a " niner " ; and it differs so much 

 from the adult form that for a long time it was supposed to be a 

 distinct animal. In place of the characteristic funnel-shaped 

 mouth the larva has a curiously formed upper lip which projects 

 like a hood, while the short lower lip is situated far back beneath 

 it, so that the opening of the mouth is horseshoe-shaped rather 

 than circular. The Lamprey lives as a larva from three to four 

 years, and spends its time buried in the mud of river beds, especially 

 frequenting quiet backwaters or slow-lowing reaches ; then during 

 the winter time it undergoes its metamorphosis, appearing in the 

 following spring as a perfect Lamprey. During its larval period 

 the Lamprey is sightless, the eyes being rudimentary and deeply 

 seated. Its food consists of minute organisms which are swept 

 into the mouth by ciliary action. 



Lampreys have an almost world-wide distribution. Most species 

 are marine, although several are found in rivers and estuaries, 

 but all Lampreys apparently ascend rivers in the spawning season 

 to deposit their eggs. They are carnivorous creatures, and appear 

 chiefly to feed on living fish, to which they attach themselves by 

 their suctorial mouth-funnel and then rasp off scales and skin 

 and flesh with the horny teeth of the tongue. They often make 

 deep holes in their victims by whom they are carried about, and 

 fishes are sometimes caught with these horrible pests still clinging 

 to their sides. So firmly do the Lampreys cling with their sucking 

 mouths to their victims that it is no easy matter to pull them 

 off, and it is said that a fish can seldom dislodge them when once 

 they have fixed themselves to its body. 



The Sea Lamprey (Petromyzon marinus), which occurs in the 

 British Isles and also frequents the Atlantic coast of North America 

 and the West Coast of Africa, sometimes reaches 3 feet, or even 

 more, in length ; the Fresh- water Lamprey (P. ftuviatilis), com- 

 monly called the " Lampern," measures about 18 inches ; and the 

 " Sandpiper," or " Sandpride," the Lesser Fresh- water Lamprey 

 (P. planeri), is seldom more than 10 or n inches long. 



The Elasmobranchii, or Cartilaginous fishes, include the Sharks, 

 Dog-fishes, and Rays an interesting and very primitive race, 

 representing the oldest type of fishes known. The fossil remains 

 of extinct Elasmobranchs tend to prove that they were in all 



