172 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 
SAENY, 
fis ee 
in Ava islets 
Fia. 119. Fic. 120. ~ Fig, 121. 
Fic. 119.—Petromyzon marinus unicolor (De Kay). Mouth of Lake Lamprey, 
Cayuga Lake. (After Gage.) 
Fic. 120.—Lampetra wilderi Jordan & Evermann, Larval brook lamprey in its 
burrow in a glass filled with sand. (After Gage.) 
Fic. 121.—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 
