72 LECTURE VIII. 



common Carp it is supposed to arrive at the age 

 of two hundred years. 



We have now passed through all the Linncean 

 orders of Fishes, but there still remains a large 

 tribe which I before mentioned under the title of 

 Cartilaginous Fishes. I also observed that they 

 differ from all other fishes in having a compara- 

 tively soft or cartilaginous skeleton, and that some 

 particularities in the structure of their gills in- 

 duced Linnaeus improperly to rank them as an 

 order of the Amphibia under the name of Nantes. 



Of the Cartilaginous Fishes the first genus is 

 that of Petromyzon or Lamprey, The character 

 is a long, round, Eel-shaped body; a mouth fur- 

 nished with numerous teeth in circular rows, and 

 seven round spiracles or breathing-holes on each 

 side the neck; these breathing-holes each lead into 

 a tubular cavity, lined with a red pleated mem- 

 brane, thus forming a series of organs analogous 

 to gills in fishes, but not quite of a similar struc* 

 ture, and more approaching to that of lungs. 

 The common or great Lamprey is an inhabitant 

 of the sea, but comes into rivers during the spring. 

 It is viviparous like the Eel, which it resembles in 



