246 



BONY FISHES 



pelvic fins function as keels to prevent rolling, but their amputation 

 in Lepomis does not produce excessive rolling. Stability in the trans- 

 verse plane is presumably assured by the dorsal and anal fins. The 



Fig. 149. Differences in form of fishes. 



A, mackerel (Scomber); B, trunk-fish (Ostracion); C, sun-fish (.Mola); D, globe-fish 

 (Chilomycterus); E, sea-horse (Hippocampus.); f, eel (Anguilla). (From Norman.) 



use of the fins for stopping was also developed in some Mesozoic 

 fishes, for instance, in the Triassic coelacanth, *Laugia, which pos- 

 sessed high pectorals, and pelvic fins in the anterior position. 



In the fishes with high pectoral fins, therefore, the pelvics are 

 usually found far forward. In the flying-fish (Exocoetus), however 

 (Fig. 151), high pectoral fins are found with posterior pelvics. In this 

 position the pelvics would tend to help rather than hinder any 



