FISHES. 



335 



lives of this group, which, however, occurs as fossils in 

 very old rocks. They have scaly bodies, diphycercal tail, 



FIG. 136. Sea-horse (Hippocampus heptagonus). After Goode. 



FIG. 137. African lung-fish (Protopterus annectens). After Boas. 



spiral valve, and a swim-bladder which is used as a lung. 

 Both pectoral and ventral fins are present, and these are 



