524 Vertebrata. 



huge Greenland or Polar Wtale (Balsena mysticetus), up to 20 m. long ; 

 in Greenland, etc. ; now mucli reduced in numbers. B. biscayensis, very like the 

 Greenland form, occurs somewhat further south (in the North Atlantic). 



Sub-Order 2. OdontOCeti {Toothed Whales). 



Furnished with teeth, but no whalebone. External nares united, 

 to form a single aperture* situated dorsally and far back on the 

 head ; several true ribs. The face portion of the skull is distinctly 

 asymmetrical; nasal bones rudimentary. Feed chiefly upon fish. 



1. Dolphins {Delphinus) have a pointed, beak-like snout, marked off from 

 the forehead by a groove; numerous (twenty or more) small conical teeth in 

 each half of the jaw; a high dorsal fin. Animals of about 3 m. long, several 

 species occur on British coasts. Allied is the S e a - h o g or Porpoise {Phocama 

 communis), 1'5 m. long, with short blunt snout, compressed teeth (about 

 twenty-five in each half of the jaw) ; abundant in European seas. The Pilot - 

 whale or Black-whale {Globiocephalus melas), has teeth only in the anterior 



Fig. 420. SkuU of a Pilot Whale, from the left side, with large mass of blubber 

 lying upon the snout ; this mass is divided medianly. / blubber, h fiim layer of connective 

 tissue below the epidermis, which is indicated by a thick black line, ■« nares, I air sinua 

 continued on from the nasal duct. — After Murie. 



portion of each jaw ; the head is thick and rounded in front, with quite a short 

 projecting pointed snout ; up to 6 m. long. It is regularly caught off the Faroe 

 Islands, and is a frequent, though irregular, visitor to British coasts. It feeds 

 principally upon Cuttle-fish. The "Grampus" or " Killer" (Orca glaAiator), 

 somewhat larger than the Pilot-whale, with very high dorsal fin (whence it is 

 sometimes termed the Sword-fish), and about twelve powerful conical teeth in 

 each half of the jaw ; feeds upon Porpoises, Seals, and Pish ; very widely dis- 

 tributed ; occurs on the west coasts of Britain. 



2. Of the more aberrant Odontoceti may be mentioned, the 

 Cachalot or Sperm-whale (Physeter macrocephalus), a. large form with 

 a huge head, on the flattened snout-like portion of which, there lies an immense 



* In the Odontoceti, but not in the Mystaoooeti, there are saccular outgrowths, both 

 from the short unpaired and also from the upper portion of the paired external nasal 

 daot. 



