1896.] 



MAMMALIAN DENTITION. 



583 



set which terminates the series. This is borne out by the discovery 

 by numerous authors (5, 7, 9, 20) of a lingual growth of the 

 dental lamina by the side of the germs of the permanent teeth. 



Fig. 1. 



Fig. 2. 



Fig. 1. — Diagram of the tooUi-succession in a polypliyodont Eeptile : 1, 2, 3, 



successive toolh-germs ; d.l, tleatal lamina. 

 Fig. 2.— Diagram illustrating the relation of a molar tooth-germ (m) to the 



dental lamina (d.l). 



Taking the above into consideration, the presence of trtie and 

 definite outgrowths from the dental lamina nearer the gum than and 

 thus labial to the molar germs is extremely interesting and suggests 

 that possibly at least one set of teeth preceding the functional 

 molars has been suppressed. These vestiges are, it is true, minute 

 and variable, but when compared with the obvious vestiges of 

 the anterior 'milk-teeth seen in Erinaceus it does seem rash to 

 conclude that these labial growths in the molar region are the last 

 indications of an earlier set of teeth. 



If this is the case, then the molar teeth are not to be referred to 

 the 1st, but rather to the 2nd dentition. 



The question then arises, is the milk-dentition the Ist set of 

 teeth ? This has been answered in the negative by Leche, and I 

 hope shortly to publish a further confirmation of this view. 



Leche (7 a) has discovered in the anterior region of the jaw of 

 Myrmecohius a minute set of teeth which precede the functional 

 set; and as the latter set are now usually regarded as the milk- 

 dentition, this vestigial series is termed the pre-milk series, and 

 meiy be compared with those small embryonic teeth seen in the 

 Crocodile (19 rt) and Iguana (8)'. 



' Rose ("Dag Zahnsystem der Wirbeltiere," Ergebnisse d. Anatomie u. Ent- 

 wiokelungsges., 1894) refers to traces of a premilk dentition in Man and 

 suggests even an earlier set of teeth in the A'^erlebrata, a remnant of the placoid 

 tooth-papilla, describing in all 5 sets, traces of at least four of which are 

 found in the Mammalia. 



