126 



LAMPREYS. 



Fig. 65. 



and ventral fins are wanting. Anteriorly, they terminate in a 

 circular, or semi-circular, fleshy lip, sustained by a cartilaginous 

 ring, formed by the solid union of the palatine and lower jaw 

 bones, or rather, cartilages. The vertebrae are reduced to simple 

 cartilaginous rings, scarcely distinct one from the other, traversed 

 by a tendinous cord, and surmounted by a second ring which is 

 more solid, surrounding the spinal marrow. There are no true 

 ribs nor branchial arches ; the branchiae, instead of being pecti- 

 nate, present the appearance of sacks formed by the union of the 

 face of one branchia, with that of a corresponding branchia on the 

 opposite side. Sometimes this imperfect* skeleton is not even 

 cartilaginous, but always remains membranous. The organs of 

 the senses are less complicated in structure than they are in 

 ordinary fishes. They have no swimming-bladder. 



21. The LAMPREYS, Petromyzoa, are recognised by seven 

 branchial openings which are seen on both sides of the neck, by 



their circular labial ring, armed with 

 several ranges of strong teeth, and horny 

 tubercles, (Fig. 65.); the tongue is also 

 furnished with teeth, and is carried for- 

 ward and backward like a piston, which 

 enables the animal to exert the faculty of 

 suction and use its buccal disk, not only 

 to suck up the juices upon which it feeds, 

 but to attach itself to solid bodies. The 

 skin of these fishes is raised up above and 

 beneath the tail in a longitudinal crest that takes the place of 

 fins, which are sustained only by vestiges of fin-rays. The water 

 necessary for respiration passes from the mouth to the branchiae, 

 by a canal situate under the oesophagus, and pierced laterally by 

 holes. 



22. The Sea Lamprey, Petromyzon marinus, ( Fig. 66. ) 

 which is two or three feet 'long, and marbled brown on a yellowish 

 ground, inhabits the coasts Fig. 66. 



of France, and the United 



States, and in the spring 



ascends rivers to deposit its 



eggs. It ordinarily preys on marine worms, and small fishes, or 



fragments of dead bodies; but it attaches itself to large fishes, 



and succeeds in piercing their skin and devouring them. Its 



MOUTH OF A LAMPREY. 



SEA LAMPREY. 



.21. What are the characters of the Lampreys ? What is the structure of 

 their mouth ? 



22. What are the characters of the Sea Lampreys? W T hat are their 

 habits ? What are the characters of fresh water Lampreys ? Where are 

 Larnprcye found ? 



