486 



CETACEA. 



a white mark over the eye in the shape of a crescent. The dorsal 

 fin is high and pointed. This is the largest of the Dolphins, being 

 frequently from twenty to twenty-five feet long. Grampuses are said 

 to attack the whale in troops, harass it until it opens its mouth, and 

 then devour its tongue. 



The Narwhals {Monodori) have no teeth in the mouth, but are 

 furnished with a straight and pointed, tusk projecting from the upper 

 jaw, and directed straight forward. The form of the head and body 

 much resembles that of the Porpoises. Only one species is well 

 known, namely, 



The Sea Unicorn {Monodon* monocerosYr The tusk of this ani- 

 mal is sometimes ten feet long, spirally twisted, and was formerly 

 thought to be the horn of the fabulous Unicorn. The Narwhal 

 possesses, however, the germs of two tusks, one on each side ; but it 

 rarely happens that both grow equally. Usually that on the left 

 side only is developed, and the other remains concealed in its socket. 

 In general, this animal is not more than twice or three times the 

 length of its tusk ; its skin is marbled with brown and white ; its 

 blow-hole is at the top of its head ; and, instead of a dorsal fin, it has a 

 ridge running along the whole length of its back. 



The other Cetacea have the head so large that it 

 constitutes one-third or even one half of their length. 

 The skull proper and the brain have nothing to do 

 with this extreme disproportion, which is altogether 



Fig. 413.— sperm whale. 



* liovos, monos, single ; ohovs, odovros, odous, odontos, a tooth. 

 t /xoi/os, monos, single ; K€f>as, ceras, a liorn. 



