186 



VERTEBRATA 



Round-mouthed Fish. There are about a dozen species 

 in this country, of which the commonest is the ocean lam- 

 prey (Petromyzon marinus) attaining a length of more than 



two feet. It as- 

 cends the streams 

 along the Atlantic 

 coast to the distance 

 of more than a hun- 

 dred miles for the 

 purpose of spawn- 

 ing, which in the 

 latitude of New York 

 occurs about the 

 middle of May. The 



FIG. 216. Photograph of the mouth of a living lam- nest is made of 

 prey sucked fast to a piece of glass. Natural size. 



gravel and sand en- 

 circled by stones nearly as large as a man's head, which 

 they suck fast to with their peculiar mouth and drag 



FIG. 217. Median longitudinal section of the anterior fourth of a lamprey eel. 

 6, brain ; c, spinal cord ; m, muscles of the back ; n, notochord ; I, liver ; h, 

 heart. Photograph. 



together. The larval young (Ammoccetes) bury themselves 

 in the mud along the banks of the streams, where they 

 remain three or four years until transformation to the adult 



