TELEOSTS. 263 



lateral line along the side of the back. Am?nodytes, sand-launces, common 

 on sandy shores. 



Sub-Order 16. Scombroidea. 



Tail diphycercal, caudal usually strongly forked ; ventrals thoracic ; 

 scales usually small, cycloid, sometimes absent; dorsal fin usually long. 

 A heterogeneous group, not easily defined; developing in three main lines. 

 ScoMBRiDiE, head normal; spinous dorsal well developed; the dorsal 

 divided up into finlets. Scomber, mackerels, first appear in miocene; 

 Thynnus, horse-mackerel, tunnies (eocene) ; Auxis (miocene), frigate-mack- 



FlG. 262. Mackerel, Scomber scombrtis. 



erel. Trichiurid^, body very long, tapering to a point ; no caudal ; 

 ventrals rudimentary or absent ; tropical. TiHchiiirns, cutlas-fishes. The 

 allied Lepidopus appears in the eocene. Pal,eorHvnchid^, extinct. 

 XlPHliD^, bones of upper jaw prolonged into a sword. Histiophorus, 

 sail-fish, possesses scales and teeth; Xz^^^zVzj, sword-fish, lacks both. Xi- 

 phiidids date from the upper cretaceous. 



CarangiD/E, pompanos of warmer seas ; caudal forked ; dorsal not 

 divided into finlets ; jaws normal. Na?tcrates, pilot-fish ; Seriola, amber- 

 fish (date from the eocene) ; Caranx, crevallds (miocene) ; Vomer and Selene, 

 moon-fishes, with greatly compressed bodies. Trachinotus, Platax, cre- 

 taceous. POMATOMID/E, blue-fish. CoRYPH/ENiD^, dolphins ; date from 

 eocene. Stromateid^, with teeth-like processes in the oesophagus ; 

 Rhombus, butter-fish ; Palinurichthys, rudder-fish. Bramid^. 



Sub-Order 17. Gobioidea. 



Dorsal spines few and weak ; ventrals thoracic, usually close together ; 

 soft dorsal and anal long; tail diphycercal. Over 600 species, mostly 

 marine, and of small size. Callionymus first appears in the miocene ; 

 Gobius (from eocene onwards) ; Clevelandia. Typhlogobius of Californian 

 shores is blind. 



Sub-Order 18. Discocephali. 



With the dorsal fin modified into a flat, transversly laminated oval 

 sucker on the top of the head ; ventrals thoracic. Introduced by Opistho- 

 myzon in the eocene of Switzerland with a smaller sucker than in recent 



