PEIMATES PEOM MADAGASCAR. 109 



The postorbital region of the frontal is curiously constricted. This, as we have 

 already had occasion to remark, is a feature recurring in all the subfossil Lemuroids. 

 The frontal region of the brain in the adult Megaladapis is itself still further 

 constricted by the presence of large aerial sinuses. 



The lower jaw is deep and massive. Its inferior outline forms in all three species 

 a nearly straight line. The mandibular suture is quite obliterated at an early age. 

 The alveolar margin of the molars and premolars is strongly curved upwards anteriorly 

 (text-fig. 24). 



The dental formula of Megaladapis is \' 2 ■ " i ■ ''m 3 ■ m 3 » ^^ ^^ adopt the theory that 

 in the lower jaw the canine functions as an incisor and that the apparent canine is a 

 premolar. 



This foi'mula, with the exception of the absence of upper incisors, corresponds with 

 the " primitive " Primate formula as found among the modern Lemuridae and the 

 CebidsB of the New World. Professor Duckworth states that the upper jaw of 

 Megaladapis insignis (== edwardsi) carries vestigial incisors. In none of the skulls 

 of Megaladapis grandidieri which I have examined is there any trace of these, unless, 

 indeed, some slight depressions in the alveolar margin of one specimen represent the 

 scars where such incisors have fallen. 



Dr. Forsyth Major has pointed out the resemblance between the teeth of Megaladapis 

 and those of Adapts magna. The tritubercular type of molar in the upper jaw is 

 most nearly represented among modern Lemurs by Lepidolemur and Chirogale. The 

 third molar of the mandible of Megaladapis is very strongly developed, having a large 

 talon. In this respect this genus contrasts with other Malagasy fossil Primates and 

 with modern Lemurs, especially the Indrisinse, where, as we have seen, this tooth tends 

 to disappear". 



In all three species of Megaladapis there is a diastema between the canine (or 

 apparent canine) and the succeeding premolar in both upper and lower jaws. 



Synonymy. — The existence of remains of extinct Primates in Madagascar was first 

 made known by Dr. Eorsyth Major, who, in 1891, published a memoir in the 

 ' Transactions of the Royal Society,' entitled " On Megaladapis, an Extinct Gigantic 

 Lemuroid from Ambolisatra." In this memoir a description is given of a skull brought 

 from the south-west of Madagascar by Mr. Last. To this the name Megaladapis 

 madagascariensis was given. 



In 1899 M. G. Grandidier described and figured in the 'Bulletin du Museum 

 d'Histoire naturelle de Paris ' three teeth of a gigantic Lemuroid on which he founded 

 the genus Peloriadapis. 



In the following year a description by Dr. Forsyth Major of a fragment of an upper 

 jaw in the British Museum appeared. To this the name of Megaladapis insignis 

 was given. 



Again, in 1906 a memoir published by Dr. Lorenz v. Liburnau, of Vienna, gives a 



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