Dr. Forsyth Major — Extinct Primates of Madagascar. 497 



The lower caniuiform tooth of Mammalia is generally anterior 

 to the upper caniniform ; if, however, for some reason or other the 

 upper premolar series should become lengthened, or the lower 

 premolar series shortened, the position of the lower ' canine ' may be 

 altered. Bateson has described and figured an instance of the first 

 kind. A skull of Ateles marg'matns in the British Museum 

 (No. 1,2146, collected by Bates) exhibits the unusual number of four 

 premolars on either side of the upper jaw. " As a consequence the 

 lower canines bite on and partly behind the upper canines." ' The 

 skull is befoi'e me : on the right side the lower canine, in fact, acts 

 on the inner side of the upper canine ; on the left side its position is 

 almost normal. 



The Cercopithecidaj, and in general all the monkeys with only 

 two premolars, are evidently derived from older forms with three 

 premolars. As often happens, the loss of the lower premolar may 

 have preceded in time that of the upper jaw, so that we may 

 imagine a transitional stage in which there were three premolars 

 above and two below. In that case the lower canine might slide 

 slightly backwards, and would in that case act on the inner side 

 of the upper canine ; this is jjrecisely the condition of things in 

 Nesopithecus and also in the majority of recent Lemuridas. When 

 finally one of the three upper premolars comes to be lost, the lower 

 ' canine ' might come again to occupy its original position in fi'ont 

 of the upper, as is the case in all Old World monkeys. 



There ai'e, therefore, as good reasons for the assumption that 

 the caniniform lower tooth of Nesopithecus and of most of the 

 Lemuridse is the homologue of the lower ' canine ' of Old World 

 monkeys, as for the generally received view. Nesopithecus has 

 approached neai'er than most of the Lemurida3 to the monkeys 

 by retaining only two lower incisors. For, of course, as a con- 

 sequence of the hypothesis propounded here, the six incisiform lower 

 teeth of the majority of Lemuridai would have to be considered 

 as the homologues of the six lower incisors of the majority of 

 Placentalia. This constitutes, for the present, its weak point, because 

 most of the Tertiary Lemuridae are supposed to have — and Adapts 

 certainly has — only four lower incisors. 



It is obvious that the position of Nesopithecus in the system cannot 

 be discussed without reference to the relations between lemurs and 

 monkeys generally. The general question being too large for 

 discussion here, I must limit myself to the following i-emarks, 



A. Milne-Edwards and A. Grandidier have, contrary to Mivart, 

 considered the Lemuroidea as forming a distinct order. Although in 

 the " Histoire de Madagascar," up to the present day, the description 

 of the Indrisinfe alone has been published, this was believed to fully 

 ^settle the question at issue. The Indrisina? being, as far as brain 

 development is concerned, the highest of recent lemurs, and thus 

 approaching, more than the rest, the Anthropoidea, the conclusions 

 as to their relationship with the latter, derived from the comparison 



1 W. Bateson: "Materials for the Study of Variation, etc.," 1894, pp. 206, 

 207, %. 38. 



DECADE IV. VOL. V!I. NO. XI. 32 



