THE LAMPREYS 3 



by an expanded circular lip or ' suctorial disc ' 

 which bears horny teeth ; at its inner edge, and 

 placed above and below, are two cuspidate horny 

 plates, which may be regarded as enlarged or 

 coalesced teeth, and are termed the supra-oral and 

 infra-oral laminaj ; within the mouth are seen the 

 lamina that arm the tongue, an anterior unpaired 

 one and a posterior pair. The eyes are subcutaneous, 

 but fairly conspicuous, and on top of the head, 

 between or a little in advance of the eyes, appears 

 the nasal opening ; the small gill-openings, seven in 

 number on each side, form a series which begins not 

 far behind the eye. The fins are two dorsals and a 

 caudal ; the former are placed behind the middle of 

 the length of the fish, and the latter is composed of a 

 long lobe both above and below at the end of the tail. 



With their suctorial disc the Lampreys attach 

 themselves to fishes, which they devour, sucking 

 the blood and scraping off the flesh by means of the 

 toothed laminae on the tongue. Whilst there can 

 be no doubt that in many respects they are a very 

 primitive group, many of their peculiarities are due 

 to their manner of life, and they may even have 

 evolved from ancestors which had jaws. All have 

 a remarkable life-history, as the larvae differ greatly 

 from the adults in structure and habits, and undergo 

 a fairly rapid transformation into the adult form 

 after some years of larval life. 



The British species are three in number, namely, 

 the Sea Lamprey (J^etromyzon marinus), the Lampern 

 or River Lamprey {LampeU^a fluviatilis)^ and Planer's 

 or the Brook Lamprey {^Lampetra planeri). The 

 larvae, known as Pride, Mud Lamprey, or Blind 



