HORSE-MACKERELS. 



447 



the palatine bones. The first dorsal with eight feeble spines 

 connected by membrane ; finlets none. Lateral line not shielded. 

 The second dorsal and anal covered with very small scales. 



Tcmnodon saltator, sometimes called " Skip-jack," is spread 

 over nearly all the tropical and sub- tropical seas ; it frequents 

 principally the coasts, but is also met with in the open sea. 

 On the coasts of the United States it is well known by the 

 name of " Blue-fish," being highly esteemed as food, and fur- 

 nishing excellent sport. It is one of the most rapacious 

 fishes, destroying an immense number of other shore-fishes, 

 and killing many more than they can devour. It grows to a 

 length of 5 feet, but the majority of those brought to market 

 are not half that length. 



Trachynotus. — Body more or less elevated, compressed, covered 

 with very small scales. Cleft of the mouth rather small, with 

 short convex snout. Opercles entire. The first dorsal composed 

 of free spines in small number. No finlets. Teeth always 

 small, and generally lost with age. 



Ten species are known from the tropical Atlantic and 

 Indo-Pacific ; they rarely exceed a length of 20 inches. Some 

 of the most common marine fishes belong to this genus, for 

 instance T. ovatus, which ranges over the entire tropical zone. 

 Pammelas {jocrciformis) is allied to the preceding genus ; 

 from the coast of New York. ^;— 



M 



r^-^ 



PsETTUs. — Body much com- 

 pressed and elevated ; snout 

 rather short. One dorsal, entireh 

 covered with scales, with seven \\ 

 or eight spines ; anal fin with 

 three. Ventrals very small, rudi- 

 mentary. Teeth villiform ; no 

 teeth on the palate. Scales small, 

 ctenoid. 



Only three species are 

 known ; one, P. scbcc, from the w^est coast of Africa, the two 



Fig. 198.- 



-Magoificil scale of Psettus 

 argenteiis. 



