168 
Litteratur. 
Arendsen Heins: Contributions to the anatomy of Monodon Monoceros. 
(Verh. d. koningl. Akad. d. Wetenschapen te Amsterdam. 1914). 
R. Brown: On the Cetaceans of the Greenland seas. (Proc. Zool. Soc. Lon¬ 
don. 1868). 
J. W. Clark: On the skeleton of a narhwal with two fully developed tusks. 
(Proc. Zool. Soc. London 1871). 
W. Kiikenthal: Vergleichend anatomische und entwicklungsgeschichtliche 
Untersuchungen an Waltieren. (Denkschr. med.-naturw. Ge- 
sellsch. Jena 1889—93). 
— Die Wale der Arktis. (Fauna arctica. I. 1900). 
M. P. Porsild: Om nogle vestgrønlandske Pattedyr og Fugle. I -II. (Medd. 
om Grønland. LVI. 1918). 
J. Reinhardt: Nogle Bemærkninger om Narhvalens Stødtand. (Vid. Medd. 
Naturh. Foren. f. 1862, 1863). 
Scoresby: Journal of a voyage to the northern whale-fishery. London. 1823. 
Summary. 
715 single tusks and 6 crania with two fully developed tusks 
were examined; they were without exception sinistrorsal. The faet 
that the tusk of the narhwal so constantly is sinistrorsal, is in 
favour of Reinhardt’s hypothesis, that there is the same course to 
the sinistrorsal asymmetry of the skuli of the whales and the 
sinistrorsal twistling of the tusk of the narhwal. It is obvious that 
all the tusks are worn at the apex, a faet to which also Porsild 
calls attention; and a great number of tusks were broken. Among 
129 tusks from Cape York 28 were broken near the base, 34 
more distally, only 67 were quite unbroken; this implies, that the 
tusk is very fragile. Often the apex was weared round and regu- 
lar, but often the wearing was more intense on one side, and there 
was then a slight concavity. When broken near the base the rup¬ 
ure was more irregular. When there were two fully developed 
tusks but of unequal length, they were both weared. I think it 
will be difficult to explain this wearing without adopting the old 
hypothesis, that the narhwal with the tusk root the sea-bottom in 
search of the food. 
24 — 1—20. 
