LAMPREYS AND HAG-FISHES. 239 



LAMPREYS AND HAG-FISHES. 



(Class: CYCLOSTOMATA.} 



THE Cyclostomata are often called the ''Marsipobranchii/' 

 in reference to their pouch-like gill-clefts. They are divided 

 into two orders ; the first of which is that including the Hag- 

 Fishes or Borers, which are chiefly parasitic upon teleostean 

 fishes, while the second is made up of the Lampreys. 



THE LAMPREYS. 



(Order: PBTROMYZONTES.} 



THE Lampreys are curious Eel-shaped animals, having a 

 large suctorial disk leading behind and above, into the 

 mouth. Numerous horny teeth are situated on the inner 

 surface of the sucker, as well as on the tongue. They all 

 belong to the one family, known as the Petromyzontidce, 

 and are distributed over the greater part of the world. They 

 are chiefly marine, some to a greater extent than others ; 

 but in those species the life history of which has been 

 closely investigated, it has been found that they ascend the 



Fig. 85. SHORT-HEADED LAMPREY (Mordacia mordax). 



rivers for spawning purposes. They are all carnivorous, 

 obtaining their food by attaching themselves by means of 

 their sucking disk to various fishes, and then rasping the 

 flesh away with the lingual (tongue) teeth. In Europe 

 and America, large numbers of fishes are known to be des- 

 troyed by Lampreys every year. 



There are two species of Lamprey in Australian waters ; 



