xii PHYLUM CHORDATA 397 



usually branching at the free ends. In many, however, the 

 anterior portions of the dorsal, ventral, and pelvic fins are 

 supported not by flexible jointed rays, but by stiff unjointed 

 sharp spines. 



The paired fins, pectoral and pelvic, are usually thin and 

 flexible, supported mainly, or exclusively, by jointed rays. 

 The pectorals always retain their normal position, just 

 behind the gill-cleft, but the pelvics always become more or 

 less shifted forwards from their typical position beside the 

 vent ; when they are not placed as far forwards as the 



Fig. 236. — SalmofariO. Caudal end of vetebral column. CN, centrum; D.F.R, 

 dermal fin-rays; H. SP, hsemal spine; H. ZYG, hasmal zygapophysis ; N. SP, 

 neural spine; W. ZYG, neural zygapophysis; UST, urostyle. 



middle of the abdomen, they are said to be abdominal in 

 position ; when further forwards, nearly beneath the pectorals, 

 they are said to be thoracic ; when still further, actually in 

 front of the pectorals and beneath the throat, they are said 

 to be jugular in position. 



A very remarkable deviation from the typical form occurs 

 in the flat-fishes (Pkuronectidm, including the soles, plaice, 

 flounders, turbots, etc.). The body (Fig. 237) is very 

 deep and strongly compressed ; the fish habitually rests on 

 the bottom, in some species on the right, in others on the 



