602 MR. J. THORNTON CARTER ON THE 



greatest development in the enamel of the tooth-cusps. With a 

 view to economy of illustration, I have not included a photo- 

 micrograph of their enamel, resembling as it does the enamel of 

 the Galagos, illustrated in PI. III. fig. 3. 



In Perodicticus potto (PI. YI. fig. 4) the penetration is not 

 nearly so rich as in the Lorises and the Galagos, whilst in 

 Nycticebus (PI, VI. fig. 3) it is but slight, many of the tubes in 

 the enamel of the molars ending just within the enamel in the 

 form of small bulbous spindles similar to those shown in the 

 enamel of Gallithrix (PI. lY. fig. 3). 



In Tarsius, concerning whose position in the classification of 

 the Primates so much has been written in recent years, the 

 penetration attains a degree of richness even greater than is 

 found in the enamel of Galago, and rivals in extent the condition 

 shown in Indris (PI. III. fig. 1). 



The actual structure of the enamel in the Lemurs also presents 

 features of great interest, inasmuch as one finds that in sections 

 of the entire tooth, the general pattern, or form and ari-angement 

 of the prisms, in the Asian and African forms differs from that 

 of the Mascarene Lemurs, and that the enamel of Tarsius is to all 

 intents and purposes identical with that of Galago. 



The pattern of the Mascarene genera is shown in the photo- 

 micrograph of a molar of Indris (PI. Y. fig. 1), and this pattern 

 is constant for all the genera, including Chiromys (PI. Y. fig. 2). 

 Immediately beneath, on the same plate, is a photo-micrograph 

 of a portion of the enamel of Semnopitliecus (PL Y. fig. 3), and it 

 will be seen that the general structure is closely similar to the 

 two lemurs, the enamel being composed of prisms or rods of a 

 somewhat granular structure and with straight, even margins, the 

 prisms being separated one from another by a slight amount of 

 calcified interstitial substance. 



The enamel pattern in the Asian and African Lemui-s is quite 

 distinct from that seen in the Mascarene forms. It is composed 

 of rods or prisms with undulating margins, which in longitudinal 

 section present a sharply-defined picture showing the wavy out- 

 line of the margins of the rods (PI. lY. fig. 1). In transvei"se 

 section (PI. YI. fig. 2) these are seen to be cylindrical rods (e.r.), 

 separated one from another by a considerable amount of the 

 calcified interstitial substance usually designated by workers on 

 the histology of enamel as the interprismatic material (i.p.m.). 



A pattern of enamel identical with this obtains in the teeth of 

 the Hapalidse and the Cebidse. In Ccdlithrix, which Gregory 

 regards as a very primitive form, there is a slight degree of 

 penetration of the enamel, the prolongation of the dentinal 

 tubes terminating in the enamel {e) in the form of little 

 bulbous spindles (6) (PI. lY. fig. 3). The close similarity of the 

 enamel pattern of Ccdlithrix, which is identical with that of all 

 other Platyri-hines, to the pattern of Galago and of Tarsius 

 will be apparent on comparing the micro-photographs figured 

 (PI. lY.). 



