492 



The Cyclostomes, or Lampreys 



narrow and toothless. From Professor Surface's paper on "The 

 Removal of Lampreys from the Interior Waters of New York 

 we have the following extracts (slightly condensed) : 



" In the latter part of the fall the young lampreys, Petro- 

 myzon marinus unicolor, the variety land-locked in the lakes 

 of Central New York, metamorphose and assume the form of 

 the adult. They are now about six or eight inches long. The 

 externally segmented condition of the body disappears. The 



FIG. 293. FIG. 294. FIG. 295. 



FIG. 293. Petromyzon marinus unicolor (De Kay). Mouth of Lake Lamprey, 



Cayuga Lake. (After Gage.) 

 FIG. 294. Lampetra wilderi Jordan & Evermann. Larval brook lamprey in its 



burrow in a glass filled with sand. (After Gage.) 

 FIG. 295. Lampetra wilderi Jordan & Evermann. Mouth of Brook Lamprey. 



Cayuga Lake. (After Gage.) 



eyes appear to grow out through the skin and become plainly 

 visible and functional. The mouth is no longer filled with verti- 

 cal membranous sheets to act as a sieve, but it contains nearly 

 one hundred and fifty sharp and chitinous teeth, arranged in 

 rows that are more or less concentric and at the same time 

 presenting the appearance of circular radiation. These teeth 

 are very strong, with sharp points, and in structure each has 

 the appearance of a hollow cone of chitin placed over another 

 cone or papilla. A little below the center of the mouth is the 

 oral opening, which is circular and contains a flattened tongue 

 which bears finer teeth of chitin set closely together and arranged 

 in two interrupted (appearing as four) curved rows extending 



