Killer. a3 
From all other Cetaceans the Narwhal (Monodon 
Narwhal. monoceros) of the Arctic Seas is distinguished by the 
peculiar character of the dentition, which is in striking contrast to 
that of its cousin the White Whale. Apart from some rudimentary 
teeth, the entire adult dentition is reduced to a single pair of upper 
tusks. In the female these remain permanently concealed in the 
bone of the jaw; and usually the right tooth of the male exhibits 
the same condition, while the left one alone is developed into a 
long spirally-twisted tusk. Very rarely, as in one of the specimens 
exhibited, both tusks may be developed. In the general contour 
of the head and body the Narwhal is very like the Beluga, but 
the skin is marked and spotted with various shades of grey. 
Narwhal feed on cephalopods, crustaceans, and fishes. The speci- 
mens exhibited include the skeleton of a male, and the skull of a 
second specimen in which both tusks are developed; the latter 
was purchased in 1885. Upon the skeleton has been built a half- 
model of the animal; and an immature stuffed specimen is 
likewise shown. In the double-tusked skull (fig. 13) it will be 
noticed that the spiral in both tusks is twisted in the same 
direction; this forms a remarkable contrast to spiral-horned 
animals, in which one horn always forms a right-handed and 
the other a left-handed spiral. Some fine specimens of Narwhal- 
tusks are exhibited on the north wall of the building. 
Killer. With the Grampus or Killer (Orca gladvator or Orcinus 
orca) we come to the first of the Delphinine, or typical 
subfamily of the Dolphin group, in all of which at least two of 
the vertebree of the neck are soldered together. Together with 
a few allied genera, the Killer (fig. 18) belongs to a subgroup 
characterised by the absence of a distinct beak to the muzzle. 
Killers are distinguished from their allies by their great ferocity, 
being the only Cetaceans which habitually prey on warm-blooded 
animals. Though fishes form part of their food, they also attack 
and devour Seals and various species of their own order, not only 
the smaller Porpoises and Dolphins, but even full-sized Whales, 
which they hunt in packs. Killers are met with in almost all seas, 
from Greenland to Tasmania, presenting much the same external 
appearance, but whether they all belong to one species is uncertain. 
They are readily known when swimming in the water by the high, 
narrow back-fin, this often attaining a still greater height than in 
the specimen shown in the gallery, which is a cast, carefully 
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