LAMPREYS AND HAGS 



6i 



the pharynx ; this, with other related conditions, has caused 

 Myxine and Bdellostoma to be inchided in a sub-group 

 of Cyclostomes, as Myxinoids, or Hyperotretcs* In each 

 genus there is possibly no more than a single valid species. 

 Myxine is a well-known form : it occurs along the Atlan- 

 tic coast at moderate depths. It is exclusively carnivorous, 



length 



It was 



Fig. 72. — A-D. Ventral aspects of heads of {A) 

 Bdellostoma (after Ayers) ; (Z?) Myxhie (after GuN- 

 THER) ; (C) Ammoccetes (after GUNTHKR) ; {D) Pe- 

 trotnyzon (after GiJNTHER). 



often boring its way into the abdominal 

 cavity of (diseased or injured) fishes, and 

 with them is brought to market ; it is 

 also taken not infrequently by line fisher- 

 men. The smallest example that has 

 thus far been described is 6 cm. in 

 recorded by Beard. (V. Ref. p. 239). 



The Lamprey, Petromyzoti, is the most perfectly studied 

 member of the Cyclostomes. Its species are common 

 to the continents of the northern hemisphere ; and in 

 South America and Australia there occur very closely 

 allied genera, as Mordacia and Geotria. The largest 

 lamprey, P. marimis (Fig. 72, and C, D), is known to 

 attain a length of nearly four feet ; it occurs in the coast 



* V. Glossary, p. 228. 



