CHAP. Ill] THE MAMMALIAN ORDER PRIMATES 43 



. The first point for remark is the retention of the Sub-order Lemuroidea. 

 Professor Hubrecht on the ground of the embryonic history and nutrition 

 ("diffuse placentation ") of the Lemuroidea, demands their rejection. Yet he 

 would retain Tarsius among the Primates. 



Professors Gadow and Elliot Smith are in favour of retaining the Lemur- 

 oidea and Tarsius, but they place the latter in an independent Sub-order, as 

 shewn in the foregoing scheme. The arguments advanced by Professor Elliot 

 Smith in favour of retention are based on observations directed to the 

 anatomy of the brain. They may be summarised as follows 1 : 



Cerebral characters indicative of the appropriateness of retaining the 

 Lemuroidea within the Order Primates 2 . 



1. The Lemuroidea agree with the Anthropoidea and differ from all 



other Eutheria in the possession of a true Sylvian fissure. 



2. The sulcus centralis is actually present in the lemurine Perodicticus ; 



it occurs in no non-primate mammal, nor in the other Lemuroidea, 

 although in these a tendency exists to the development of a furrow 

 limiting caudally the motor area (as does the sulcus centralis). 



3. The motor area of the cortex resembles histologically that of the 



Anthropoidea and has a similar topographic distribution. 



4. The sulcus calcarinus and the distribution of the visual area conform 



precisely to the type found in the Anthropoidea, though in some 

 respects affinities to the Carnivora are shewn. 



5. The characters of the cerebellum present corresponding resemblances 



to those met with in the Anthropoidea. 



6. The evidence nevertheless assigns to the Lemuroidea a lowly position 



in the Order Primates. 



The second point to be discussed is the dissociation of the Tarsii from the 

 Lemuroidea. The former provide several interesting links between the Lemur- 

 oidea and the Anthropoidea, as will be explained in the sequel (p. 105). The 

 Family Pithecanthropidae is a provisional one, and to it are referred (a) the 

 Javanese fossil remains called Pithecanthropus erectus 3 , and (b) the Mauer 

 jaw from Heidelberg 3 . 



Within the Hominidae, the cranial fragments recently discovered (1912) 

 by Messrs Smith-YVoodward and Dawson in Sussex (the Piltdown skull) are 

 claimed as distinctive of a separate genus (Eo-anthropus dawsoni), while the 



1 The following memoirs should be consulted : 



1. Elliot Smith, Linn. Trans, vol. vra, Part 10, p. 417. 



2. ,, Lin. Soc. Journal, vol. xxix, pp. 80 — 89. 



3. ,, Nature, 1907, May 2, p. 7. 



4. ,, Brit. Assoc. Report, 1908, p. 875. 



5. ,, Nature, 1909, p. 38. 



6. Standing and Elliot Smith, Zool. Trans, vol. xvm, Part 2, 1908, p. 59. 



2 Elliot Smith. No. 3 of preceding note. 



3 v. Chapter xvn. 



