338 



XXX. FAMILY OF THE LAMPREYS. 

 PTEROMYZID.E. 



Representatives in British Fauna. Gen. 4, Sp. 0L 



Gen. 1 22. PTEROM YZON. Sp. 24 8. P. marinus. The Lamprey, 



249. P.fluviatilis. River do. 



250. P. Planeri. Planer's do. 



123. AMMOCCETES. . 25 l.A.lmncJiialis. Pride, or Mul 



do. 



124. GASTROBRANCHUS.252. G. CCBCW. . Myxine, or Gliv 



tinous Hag. 



125. AMPHIOXUS. . 25 3. A.lcmeeolatus. Lancelot. 



This group forms Cuvier's second family of Chon- 

 dropterygian or cartilaginous fishes with fixed bran- 

 chiae. The species resemble eels in the elongated 

 and rounded shape of the body, and the resemblance 

 also holds in relation to some of their habits. In 

 t,he typical species the branchial cells and gills 

 \vithin them are situated along the side of the neck, 

 and there are seven apertures leading to them by 

 which the water is admitted and expelled. The 

 mouth is circular, armed with hard tooth-like pro- 

 cesses, and provided with a flexible lip. This mouth 

 readily admits of being employed as a sucker, and 

 as the species are destitute of a swimming-bladder, 

 as well as pectoral and ventral fins, and are there- 

 fore imperfectly fitted for swimming, they often fix 

 themselves by means of it to stones, and thus relieve 



