HIPPOPOTAMUS. 11 



of opinion. Owen 1 considered that the first and second incisors of both jaws were 

 those represented; de Blainville, 2 on the other hand, av rites : "Dans le tres-jeune 

 age, il est certain qn'il y a trois paires d'incisives en haut comme en bas, et que 

 ces incisives sont beancoup pins subegales, dont nne paire excessivement petite 

 n'est pas remplacee, la premiere superieurement, la troisieme inferieurement." 

 Lydekker, 3 arguing from the fact that i. 2 in If. palseindicus is very small and 

 apparently about to disappear, considered that this was the tooth which is missing 

 in II. am.phibius and that by analogy 1. 2 is also missing. 



The following table shows the views of tin 1 various authorities on this point : 



Owen and most authors considered the teeth represented to be . i. 1 and 2 and i. 1 and 2 

 de Blainville considered the teeth represented In lie . . . i. 2 and 3 and i. 1 and 2 



Lydekker considered the teeth represented to he . . . . i. 1 and 3 and i. 1 and 3 



De Blainville's statement as regards the lower milk-incisors is confirmed by an 

 examination of a very young mandible (1873) in the Museum of the Royal College 

 of Surgeons. In this mandible there arc two small incisors, d.i. 1 and d.i. 2, and 

 in the wide gap separating d.i. 2 from the canine is an alveolus in which the 

 germ of d.i. 3 can be distinctly seen (PI. V, fig. 17). 



Another mandible in the Royal College of Surgeons Museum, that belonging to 

 the skeleton (no. 1872) of a male hippopotamus two days old, shows a distinct pit in 

 the position of d.i. 3, but there is no tooth-germ in it. The germ might, however, 

 easily have been lost in preparation. The wide gap separating the outer incisor 

 from the canine in the adult skull also suggests that the tooth lost is the 3rd 

 incisor. An examination of two young skulls in the College of Surgeons Museum, 

 and of one in the Museum of Zoology at Cambridge, does not, however, lend any 

 support to de Blainville's view that i. 1 is the missing upper incisor in the adult. 

 The very young skull (M. 10702) at Cambridge shows what is apparently the 

 alveolus of d.i. 3 between the canine and d.i. 2. The skull of the male 

 hippopotamus (no. 1872) two days old in the College of Surgeons Museum shows no 

 trace of d.i. 3. It seems best to adhere to the view ordinarily accepted that the 

 missing incisors in the adult hippopotamus are i. 3 and i. 3. The fact* that 

 occasionally examples of //. amphibius are met with possessing three incisors 

 should be noted, though this need not necessarily imply reversion. Falconer 4 

 refers to a specimen at Dublin with three incisors in the right mandible and two in 

 the left, Graudry 5 to a specimen at Paris with three incisors in the right and two in 

 the left premaxilla. 



Note. — Dr. C. W. Andrews very kindly examined the skulls at the Royal College of Surgeons 

 Museum and agreed (hat in the mandible no. 1873 the germ of d.i. 3 is present. 



1 ' Odontography,' p. 563. 2 ' Osteographie,' vii, p. 32. 



3 ' Palseont. Ind.,' iii, p. 48. i ' Palseont. Mem.,' ii, p. 406. 



5 'Bull. Soc. Geol. France,' [3], iv, p. 504. 



