STRUCTURE OF THE ENAMEL IN THE PRIMATES. 603 



I have prepared sections of teeth of Megaladapis grandidieri 

 and of PalcBopropiihecus from the Pleistocene of Madagascar. 

 In the former penetration was almost absent, but in PalcEopropi- 

 thecus a system of tube is present, developed to an extent which 

 equals the condition seen in the teeth of Frojnthecus itself 

 (PL II. fig. 3). 



In pattern both forms have an enamel identical with that of 

 the recent Mascarene forms. 



The microscopical examination of the enamel in Primates 

 therefore discloses certain features which have not been noted 

 before. They are : — 



(1) The enamel in all Lemurs, with the exception of Chiromys^ 

 possesses a system of tubes continuous with the dentinal tubes. 

 In Indris and Propithecus the penetration is very rich, but in the 

 Lemurinfe it is feebly developed. In the Galagos, the Lorises, 

 and in Perodicticus potto the penetration is rich also, but in 

 j^ycticehus it is slight, so slight, in fact, that except in the apices 

 of the cusps, the penetration is reduced to a degree which is but 

 little greater than one finds in the teeth of the ISouth American 

 monkeys. 



(2) There is a mai'ked and constant difference between the 

 enamel pattern in the Mascarene forms and the Asian and 

 African forms, the enamel in the former having a pattern 

 identical with that found in the Catarrhines, whilst the Asian 

 and African forms present a pattern identical with that seen in 

 the teeth of the Platyrrhines. The Lemuroidea, therefore, parallel 

 the Anthropoidea in enamel structure. 



(3) Tarsius has an enamel indistinguishable in sections from 

 that of Galago. 



Amongst living mammals the penetration of the enamel by 

 tubes is, as alreai^y stated, a character found in all Marsupials, 

 Phascolomys excepted. No other order possesses this character 

 as a constant feature of all its genera. 



In the order Insectivora, however, there are a number of 

 genera which do possess it. In the Menotyphla one finds an 

 extremely rich penetration in the enamel of the Macroscelidae 

 {Petrodroimis and Rhyncocyon were examined), but in sections 

 prepared from a large number of teeth from skulls of Tupaia 

 there is no trace of any penetration. In the Lipotyphla all teeth 

 of Soricinae and of Orocidurinse have enamel which is richly 

 tubular. Erinaceus has a moderate degree of penetration, but 

 Gymnura has none. The Talpinfe also do not disclose any 

 penetration. 



The two genera comprising the suborder Hyracoidea have an 

 enamel which is richly tubular. 



The only other living mammal which possesses this character 

 in the enamel is the Jerboa, one solitary creature out of the large 

 number comprising the order Rodentia. 



In the enamel of the teeth of all fossil Marsupials which I have 



