PEIMATES EEOM MADAGASCAE. 



101 



and the summit of the bulla, in other cases the condition resembles that seen in 

 A. majori. 



Very great differences exist in the proportions of the various regions of the skull, 

 the extreme examples diverging so widely as certainly to justify their classification as 

 distinct species did not intermediate forms exist which make such a differentiation 

 impossible. We have seen that the genus Pal(BOj)ropithecus presents the same 

 phenomenon. This extreme variability would appear to be a mark of species 

 approaching extinction. 



Dentition. — The great variability in the dentition has already been referred to. 

 The occurrence of a triangular third molar was, as above stated, considered by 

 Dr. Grandidier of sufficient importance to form a new genus, Bradylemur ; but we 

 have seen that in point of fact even specific distinctions cannot be based on the 

 character of this tooth (see Plate XVI.). The first and second molars also show 

 considerable variations in form. In some cases the transverse furrow which separates 

 the tooth into anterior and posterior halves is continued by a strongly marked vertical 

 groove, which again is confluent with the interstice between the anterior and posterior 

 roots of the tooth. In some specimens, again, this vertical furrow is entirely absent, 

 the tooth presenting one unbroken convex internal surface. Here, too, however, an 

 intermediate form exists, so that it is impossible to use this character for purposes of 

 specific distinction. 



Eeference has been made to the varying proportions and the length of the series of 

 molars and premolars respectively ; the fact of this variation will be apparent if 

 expressed in tabular form thus : — 



Length of Eatio of molars 



three premolars. to premolars, 



mm. 



Length of 



three molars. 



mm. 



.. 24-6 



.. 27-5 

 . 23-5 



.. 24 



.. 23 



.. 25-2 



.. 22 



. . 24-6 



.. 26 2 



25 

 25 



26 



26-3 



25 



26-8 



25-7 



27-6 



28-8 



•98 

 1-10 

 •90 

 •91 

 •92 

 •94 

 •85 

 •89 

 •91 



The amount of backward extension of the whole dental series again is subject to 

 much variation, the third molar in some instances almost abutting on the pterygoid 

 fossa, while in other cases a distance of more than a centimetre intervenes. The 

 interval between the third molar and the auditory bulla varies in different specimens to 

 the extent of nearly 15 mm. The posterior margin of the palate has a deep U-shape, 

 its central portion being so far forward that it is generally opposite the first molar. 

 The individual teeth closely resemble those of A. majori, the chief variations occurring 

 in the molars. The median pair of incisors are stronger and larger in proportion 



p2 



