VERTEBRATES I FISHES. 



scarcely differing from one another. But one of the most 

 characteristic features of these animals is the tongue, 

 which moves forwards and backwards like a piston, en- 

 abling them to produce a vacuum, and thus fix themselves 

 to solid bodies as well as to fishes. 



PETROMYZONIM:, OR LAMPREY FAMILY. This Fam- 

 ily comprises the Lampreys and their allies. The Genus 

 Petromyzon has the maxillary ring armed with strong 

 teeth. The American Sea Lamprey, P. americanus, LeS., 



is from two to three feet long, 

 ending behind in a sharp tip. 

 It ascends rivers, and piles 

 up heaps of stones, among 

 which it lays its eggs. The 

 Bluish Sea Lamprey, P. nigricans, LeS., is five to seven 

 inches long, and is found attached to cod, haddock, and 

 other fishes. 



The Genus Myxine contains low forms, which Linnae- 

 us classed with worms. The 

 Hag, M. limosa, Girard, is from 

 six to eight inches long. It 

 is common in the waters about 

 Grand Menan. 



Lamprey, P. americanus, LeS. 



Fig. 247. 



Hag, M. hmom, Girard. 



Fig. 248. 



The Genus Branchiostoma, Amphioxus of authors, con- 

 tains animal forms which 

 are considered the lowest 

 of all vertebrates. Several 

 species are known, one of 

 which is found on the At- 

 lantic coast of the Southern States. 



Fossil fishes are found in all the systems of rocks from 

 the Silurian upward, and their history, as written by 

 Cuvier, Agassiz, and others, is full of instruction and in- 

 terest. 



Lancelot, Amphioxus, nat. size. 



