198 MARINE AND FRESHWATER FISHES 



by a basket-like cartilaginous framework ; no pectoral or 

 pelvic limbs ; branchial apparatus consisting on each side of 

 seven sacs, which open externally by as many distinct aper- 

 tures and communicate on the inner side with the pharynx. 

 The Lampreys, which may be said to represent the 

 lowest recognisable order of true fishes, are easily distin- 

 guished by their eel-like contour, the peculiar form of their 

 jawless mouths, which are usually so modified as to form 

 a powerful adhesive sucker, by their want of pectoral and 

 ventral fins, and by the numerous gill-openings developed 

 along the sides of the head. Of British representatives of 

 this order there are as many as four species. Of these the 



FIG. 32. LAMPREY {Petromyzon martnus). 



Sea Lamprey (Petromyzon marinus\ No. 228, is a large 

 form growing to a length of two or three feet, and mottled 

 with yellow and black much after the manner of the 

 Murcena. Although passing most of its time in the sea, it 

 migrates in the spring months up our larger rivers to spawn, 

 and is often at such seasons taken in large quantities. A 

 fine specimen of this fish is shown in the Day Collection. 

 The River Lamprey or Lampern (Petromyzon fluviatilis\ 

 No. 229, a smaller species, rarely exceeding a length of twelve 

 or fifteen inches, colour slate grey above and whitish beneath, 

 is still tolerably abundant in the Thames, and was formerly 

 exported alive in prodigious quantities for the purposes of 



