ae ELASMOBRANCHII—SELACHII 455 
The more typical representatives of this family are the Spiny 
Dog-Fishes, which are distinguished by the presence of a strong 
spine in front of each dorsal fin. They are more abundant in 
temperate regions than in the intervening tropics. The more 
important genera are Acanthias,Centrina, Centrophorus, Spinaz,and 
Centroscyllium. Acanthias vulgaris, the Picked or Piked Dog- 
Fish, is a gregarious, voracious Shark, about 3 to 4 feet in 
length, and is frequently seen in huge shoals all round the 
British coasts, especially during the summer months. It is very 
destructive to food Fishes, and its ravages result in serious loss 
to fishermen. -Acanthias is viviparous. Centrina salviani is a 
much smaller Shark, which frequents the Mediterranean and the 
Bay of Biscay; on rare occasions it has been taken off the 
southern coast of England. Centrophorus occurs in deep water 
in the Mediterranean and adjacent portions of the Atlantic, and 
off the coasts of Japan. Centroscylliwm is found on opposite 
sides of the North Atlantic (Greenland and Massachusetts), and 
in the opposite hemisphere at the Falkland Isles. A deep-water 
form, Paracentroscyllium, has been obtained in the Bay of Bengal 
at depths from 285 to 405 fathoms." 
Three remaining genera (Scymnus, Laemargus, and Echino- 
rhinus) differ from the preceding in the absence of dorsal spines. 
Scymnus lichia is common in the Mediterranean and the neigh- 
bouring parts of the Atlantic. The Greenland Shark (Laemargus 
Fic. 260.—The Greenland Shark (Laemargus borealis). (From Goode and Bean. ) 
borealis) (Fig. 260) is an inhabitant of the Arctic regions, wander- 
ing as far southwards on opposite sides of the Atlantic as 
the French coast and Cape Cod. It is a huge, clumsy shark, 
reaching a length of 26 feet. Numerous instances are recorded 
of its capture off the coasts of Great Britain, especially in northern 
waters. The Greenland Shark is said to be a determined foe to 
1 Alcock, Ann. Mag. Nat. Hist. (6), iv. 1889, p. 379. 
