FLOWER. — ARCTIC CETACEA. 43 



gum. Nearly black, paler on the belly. Dorsal fin small and 

 falcate. Length 20 to 26 feet. A rather common and well- 

 known species, ranging, according to season, from the mid 

 Atlantic to Davis Straits. 



Skeletons of larger size and with greatly developed crests on 

 the maxillary bone are assigned to a second species, H. latifrons^ 

 Gray, though some zoologists think these are only very adult 

 males of the former. This is an important point to determine. 



Allied to Hyperoodo7i are two very important species, Ziphins 

 cavii'ostris, Cuv., and Mesoplodon Sowerbiensis, Blainv., about 

 which there is still much to be learned. They have both been 

 found in the North seas, the former near Shetland, and the latter 

 on the coasts of Scotland and Ireland, though not at present known 

 to range farther norf.h. The Cetaceans of this group (the Ziphioids) 

 are known by the absence of teeth in the upper jaw, and their small 

 number, (two to four), in the lower jaw, and by the small rounded 

 form of the pectoral fins. 



The remaining Northern Cetaceans belong to the family of 

 true Dolphins {DelphinidcE), 



The Narwhal, Monodon monoceros, Linn., distinguished by the 

 absence of dorsal fin and the well-known and peculiar dentition. 

 A truly Arctic animal. The function of the projecting tusk is not 

 satisfactorily ascertained. Every attempted solution of the problem 

 must bear reference to its being present only in the male sex. 



Delphinapterus leitcas (Pallas). The Beluga or White Whale, 

 Kellelluak of the Greenlanders, also a genuine Arctic species. It 

 closely resembles the Narwhal in external characters (absence of 

 dorsal fin, &c.), and in its skeleton, but differs in dentition, having 

 8 to 10 teeth above and below on each side. Length 12 to 14 feet. 

 All the Northern Belugas are generally considered to belong to 

 one species, but Cope, from the examination of skeletons, has dis- 

 tinguished and nam^d four or five. The subject requires further 

 investigation. 



Genus Orca^ Gray. The Killer or Grampus, Ardluk of the 

 Greenlanders. Easily known from all other Cetaceans, even 

 when swimming in the water, by the high narrow dorsal fin, and 

 on closer inspection by the broad rounded pectoral fin or flipper, 

 and the large, strong conical pointed teeth, 11 or 12 on each side 

 above and below. Black above and white below, the colours 

 being sharply defined and arranged in a definite pattern. Length 

 20 to 25 feet. Whether all the Killers of the Northern seas belong 

 to one species ( 0. gladiator, Lacep.) or to several, is still a problem 

 which can only be solved by a large collection of skeletons, accom- 

 panied by careful descriptions or drawings of the external cha- 

 racters of the same individuals. See D. F. Eschricht, " On the 

 Northern Species of Orca," Recent Memoirs on the Cetacea, Ray 

 Society, 1866 ; J. E. Gray, " Supplement to the Catalogue of the 

 " Seals and Whales in the British Museum, 1871." 



Pseudorca crassidens (Owen). Teeth very like those of Orca, 

 but it is distinguished from the true Killer by its smaller size., 

 narrower flipper, shorter dorsal fin, and more uniform dark colora- 

 tion. Hitherto only met with in a subfossil state in Lincolnshire, and 



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