26 
ZOOLOGICAL LITERATURE. 
Only once another animal was found in the stomach, viz. a gigantic Priapulus 
caudatus. Young Walruses, more than a year old, with tusks from ^ to 1 
inch long, are unable to obtain the same kind of food, hut continue to suck 
the old females, whose udders are full of milk. The time of copulation occurs 
in the end of May or in June ; the female is with young for nearly a year ; 
it suckles it for nearly two years — that is, until the tusks of the young have 
grown to the length of 3 or 4 inches, when it can obtain its food, inde- 
pendently of the mother. As long as the young is very tender, the mother 
lives isolated from the rest j hut afterwards the mothers congregate in herds. 
No copulation takes place during the two years of lactation ; therefore it is 
evident that the Walrus propagates its species only every fourth year. The 
sexes form separate herds, the females, with their offspring, living closer to the 
shore than the males. The Walrus has no intestinal worms. (CEfvers. Svensk. 
Vetensk. Akad. Forhandl. 1864, p. 130.) 
The same author has examined the milk-teeth of the Walrus (CEfvers. 
Svenski Vetensk. Akad. Forhandl. 1864, p. 505), and figured the dentition o^ 
an embryo (on pi. 7). He thinks that the skull examined by Wiegmann 
showing five molar teeth in the upper jaw must have been abnormal, and 
that Wiegmann had come to erroneous conclusions. In the embryo observed by 
Hr. Malmgren, the formula of teeth would be ~, — j y, The following 
of these teeth disappear first, and already before birth, either all, or at least 
for the greater part : — the inner pair of incisors of both jaws, the first pair of 
molars of the upper, the second of the lower jaw, and the third pair of 
molars of both jaws. A short time after birth, or at the commencement of 
the period of lactation, the following are lost : — the middle lower incisors, the 
upper and lower canines, the first pair of lower molars, and subsequently the 
second pair of upper molars, and the outer incisors of both jaws. The middle 
incisors of the upper jaw and the fourth pair of molars of both jaws are the 
teeth which remain longest, but these also are usually lost before the animal 
commences to be independent of the mother — that is, two years after birth. 
One or the other pair of the teeth mentioned last may remain to the third 
or fourth year j but this is the exception, and they are never found in old 
and full-grown individuals. 
The permanent teeth are already developed in the foetus, y, yj y, y. 
In consequence of this paper. Prof. Peters was induced to examine the 
skull of a specimen with milk-teeth from Labrador, about eighteen months 
old (Monatsber. Acad. Wiss. Berl. 1864, p. 685). He figures the jaws, and 
shows that Hr. Malmgren was rather too hasty in declaring erroneous the 
formula for the milk-teeth which had been generally adopted since it had 
been given by Wiegmann, viz. y, yj y; y, y. The Labrador skull has the 
five upper molars most distinct, and so regularly placed that none of them 
can be considered abnormal. 
Prof. Peters says that the knowledge of the number of milk-teeth is im- 
portant in this genus, because only thus the presence of those supernumerary 
teeth can be explained which are found in adult animals, and which are 
nothing else but milk-teeth abnormally developed at a later period of the 
growth of the animal. He observes that Fremery had already observed the 
presence of five molars, founding a second species chiefly on this character. 
A Mr. A. Newton strongly urges to renew the experiment of obtaining young 
