DENTITION. 55 



According to Peters, Malmgren, from not finding more than 

 four upper back-teeth in any of the many skulls of various ages 

 he had examined, concluded that when a fifth is present it is 

 abnormal. The young skull figured and described by Peters, 

 however, has in the upper jaw the fourth and fifth back- teeth 

 still in place on the right side, and the fourth on the left side, 

 with an alveolus of a fifth. This Peters considered as affording 

 new proof of the correctness of Wiegmann's formula. As 

 already noticed, five molars have been recognised by Fremery, 

 Eapp, Giebel, and Owen, and, though perhaps not always pres- 

 ent, are frequently to be met with. 



The dental formula of the Walrus, as determined by Eapp 

 and Wiegmanu, has been adopted by Van der Hoeven * and 

 Blasius, t as well as by Peters, and essentially by Giebel. Gie- 

 bel, however, gives only four deciduous lower incisors, instead 

 of six. Owen, in his later works, agrees in this point with Gie- 

 bel, but takes apparently no cognizance of the deciduous fourth 

 and fifth molars, to which he refers, however, in his earlier 

 papers. 



Gray, f in 1866, although quoting the formula given by 

 Eapp, adopts the following : " Cutting teeth -| in young, in 

 adult 5 grinders ~^ in adult, truncated, all single-rooted ; ca- 

 nines, upper very large, exserted." He, however, quotes Eapp's 

 formula, and also that given by Owen in his " Catalogue of the 

 Osteological Series of the Museum of the Eoyal College of Sur- 

 geons" (1853, p. 630). 



Professor Flower, in 1869, gave a diagram of the dentition of 

 the Walrus based on many observations made by himself and 

 on " those of others, especially Professor Malmgren," in which 

 both the temporary and permanent dentition is indicated as fol- 

 lows : Milk dentition : I. |=|, C. i=J, M. J^ j permanent denti- 

 tion: I. =. C. i=^, M. |=|. He adds that it is probable that 



0' 1 X' o <> 



an anterior rudimentary incisor is developed in the upper if not 

 in the lower jaw," making the temporary incisors hypotheticaUy 

 f^f . " I believe," he says, " that the rudimentary milk teeth 

 never cut the gum, and are absorbed rather than shed. This 



process commences before birth, The rudimentary teeth, 



however, in front of and behind the large teeth are not 



* Lehrbuch der Zoologie, 1856, p. 733, English ed. 

 t Sikigcthiere Deutschlands, 1857, pp. 261, 262. 

 t Cat. Seals aiid Whales, p. 35. 

 $ Jouru. Auat. and Phys., iii, p. 272. 



