CATALOGUE OF VERTEBRATES. 659 



Fishes with cartilaginous skeleton ; heterocercal tail ; no air-blad- 

 der ; embryo with deciduous external gills. 



Section SELACHII. 



(Plagiostomi.) 



ORDER SQUALL 



Sharks. 



Famly SPIHACIDJE. 



Dogfishes. 



Body elongated ; head depressed ; eyes lateral, without nictitating 

 membrane ; mouth and nostrils inferior ; five gill openings on each 

 side ; two dorsal fins with spines ; no anal fin. 



SQUALUS, L. 



(Acanthias, Risso.) 



S. acanthias, L. (americanus, Stor., sucklii, Grd.^ Spiked Dogfish. 

 Bone Dog. Skittle Dog. Hoe. 



Body slender ; snout pointed ; head, 6 J inches ; slate color 

 above, with white spots on back ; pale below ; teeth small, alike 

 in both jaws; spiracles wide, just back of eyes; gill openings 

 narrow. Length, 12 to 36 inches; weight, 5 to 15 pounds. 

 Their livers valued for oil. 



" This is a common species along our coast, and according to 

 Storer, are so numerous at Gape Cod as to form an important 

 fishery for the oil they furnish." 



