52 ODOB^ENUS ROSMARUS ATLANTIC WALRUS. 



Jaeger,* in 1844, described the dentition of three rather young 

 Walrus skulls from Labrador. In the youngest skull (8 inches 

 long, 6 inches broad, Paris measure), which had the Canines 

 about two inches long, he notes that the last upper molar had 

 already fallen from the right side, but still remained on the 

 left, behind which, as well as behind the alveolus of the fourth 

 molar on the right side, was a little shallow pit, in which, dur- 

 ing fretal life, a tooth had perhaps stood. In front of these 

 beforementioned teeth were three molars on each side, and in 

 front of these a conical incisor, and the alveoli of the others 

 were traceable, although already filled with a spongy substance. 

 In the lower jaw, there were five teeth on each side, with traces 

 of three already fallen foetal incisors on one side and of two on 

 the other. The second skull (9 j inches by 7) was somewhat 

 older, the canines being about five inches long. There were 

 present in this skull three upper molars on each side, and a 

 filled-up alveolus behind them. Of these teeth (as also in the 

 other skull), the middle one was the largest and most worn.t 

 In front of these, and somewhat distant from them (5'"), was an 

 incisor on each side, and in addition to these another pair of small 

 conical incisors. In the lower jaw of this skull were, on each 

 side, four teeth homologized as C. 1 1, M. 3 3; Jaeger thus 

 recognizing, as had Kudolphi, Eapp, Wiegmann, Fremery, and 

 Stannius, the first of the lower-jaw series as a canine. Behind 

 these were traces of the alveoli of the fourth pair of molars. In 

 the third skull (length 12 J inches, breadth 10 J), still older, with 

 tusks a foot long, were three upper " back-teeth " on each side, 

 close together, the middle one being the largest, and in front of 

 these a cutting- tooth. The lower jaw had also four teeth on 

 each side, homologized as before. In this skull, there remained 

 no trace of the middle incisors. Another still older skull had 

 the same dental formula as the last. 



Owen,f in 1853, gave the following formula for the deciduous 

 dentition of the Walrus: I. |5|;C.i5-J; M. 5-2=18. Thiswas 

 based on the examination of a young animal, which had 

 died in the Zoological Gardens of London. He, at the same 

 time, proposed the following as the formula of the normal or func- 

 tional dentition of the Walrus: I. i=-J; O.J; Pm. 5-3=18. 



* Miiller's Arch., 1844, pp. 70-75. 



t In the young skulls described by Stannius, the middle molar is mentioned 

 as being uniformly the largest and most worn. 

 t Proc. Zool. Soc. Lond., 1853, pp. 105, 106. 



