STRUCTURE OF THE ENAMEL IN THE PRIMATES. 607 



Tarsius has an enamel richly tubular, and in its structure 

 essentially Lemurine. 



A furthei" interesting feature is that the pattern of the enamel 

 in the Mascarene Lemui^s difiers from that of the Asian and 

 African foi-ms, and that the former has a structure identical with 

 that found in the enamel of all Catarrhines, whilst the structure 

 of the enamel in the Platyrrhines is identical with that found in 

 the Asian and African Lemurs. 



Two primitive Lemui'oid Primates, Pelycodus and JS'otharctus, 

 from the Eocene show no penetration, but in the structure of 

 their enamel resemble the Mascarene Lemurs. 



Hemiacodon, a Tarsioid Primate, also from the Eocene, has an 

 enamel which is tubular, and in structure appears identical with 

 the enamel of the recent Tarsius. 



The enamel pattern affords a useful test of affinity if taken in 

 conjunction Avith the character of a tube-penetration, and enables 

 one to discriminate between Multituberculates, Marsupials, and 

 Placentals. 



EXPLANATION OF THE PLATES. 

 The followiua; is a list of reference letters common to the various figures : — ■ 



h. bulbous spindles. 



d. dentine. 



e. enamel. 



e.r. enamel rods. 



h.s. horseshoe- shaped bodies. 

 i.p.m. interprismatic material. 

 u.l. uncalcified layer. 



Plate I. 



Fig. 1. Longitudinal section through the incisor of Indris, showing the pi-esence in 

 the enamel (e) of tubes {t) continuous with those of the dentine. X 180, 



Fig. 2. Longitudinal section through the protocone of an upper molar of Indris, 

 showing a similar condition to that seen in tig. 1. X 180. 



Plate II. 



Fig. 1. Longitudinal section of a lower incisor of JLemur catta, showing the form and 

 structure of the enamel rods or prisms (p), and at the surface of the 

 dentine {d) next the enamel a layer of uncalcitied material {u.l.). X 350. 



Fig. 2. Longitudinal section of a lower mcisor of Lemur, showing the passage of 

 tubes {t) from the dentine {d) into the enamel (e) ; the tubes traversing 

 the layer of uncalcitied material {u.h) are shown in fig. 1. X 350. 



Fig. 3. Section of a lower premolar of Propitheciis, showing the presence of tubes {t) 

 in the enamel (e). X 300. 



Plate III. 



Fig. 1. Section of a tooth of Tarsius, showing the junction of the tubes (t) in the 



enamel (e) with those of the dentine {d). X 450. 

 Fig. 2. Section of a lower incisor of Microcelms. X 250. 

 Fig. 3. Section from the coronal surface of a lower molar of Galago. X 350. 



Plate IV. 



Fig. 1. Section of a tooth of Tarsius, showing the general pattern of the enamel (<?) 

 with the undulating margins of the enamel rods {e.r.) and the tubes {t) in 

 the enamel. X 350. 



Fig. 2. Section of a tooth of Galago, presenting an appearance identical with that 

 shown in fig. 1. X 340. 

 • Fig. 3. Section of a premolar tooth of Callithrix {Callicebus), showing an enamel 

 pattern similar to Tarsius and to Galago. The dentinal tubes terminate 

 a very short distance within the enamel as little bulbous spindles (6). 

 X 350. 



