CLASS I. 

 CARTILAGINOUS FISHES 



ORDER I.— CYCLOSTOMI. 



GEN. PETROMYZON. 



Sea Lamprey. — Petromyzon Marinus. Like 

 the eel family, in general, the lamprey has a long, 

 flexible, slender body, covered with an oily excre- 

 tion, admirably fitting it to slide into dark, 

 and oftentimes difficult hiding places. It is 

 unsocial in its habits, — timid in the day-time, but 

 voracious, courageous and unyielding in the night, 

 when it ventures from its lurking place, in search of 

 food. The size to which they grow in the arms 

 of the sea, in the limits of Massachusetts, particu- 

 larly, is not great, nor are they commonly more 

 than two feet in length. As the traveller, howev- 

 er, follows the southern shore, he not only finds 

 the sea lamprey much thicker, but also much long- 

 er. Three feet may be considered an average 

 length in the southern states, but the saltness of the 

 water and its coldness, so far to the north, is unfa- 

 vorable to their multiplication, as well as magni- 



