IN THE EXTINCT LEMUES OF MADAGASCAE. 175 



[coronal] sulcus seems to be brokeu into two parts — the true inferior frontal and the 

 sulcus " e." 



One of the most interesting features of this brain is the conformation of the Sylvian 

 region. In the left hemisphere we have an exact reproduction of that peculiar 

 grouping of furrows which is found in the Primates only in Chiromys [see especially i, 

 fig. 33, p. 356]. The apparent " Sylvian " sulcus is merely pseudosylvian (fig. 63, 

 s.ps,), as this occurs in the Carnivora, and the inverted U-shaped furrow which 

 surrounds its upper end represents a combination of the suprasylvian sulcus (anterior 

 limb) with the postsylvian sulcus (posterior limb) — figs. 61, 62, and 63, ss. and s.temp.sup. 

 respectively. The relations of the cerebellum to the hemisphere are like those of 

 Chiroinys. 



On certain Affinities of the Indrisinje. 



The conclusions drawn by Dr. Forsyth Major (' Geological Magazine,' decade iv. 

 vol. vii. No. 437, p. 494, November ]900) from the features of the teeth and skeleton 

 agree so closely with the clear evidence of the cerebral characters that they are worth 

 quoting here : — " As to the aflanities of Megaladains with other Lemuroids, I now hold 

 that its specialisations are not a sufficient reason for its being removed into a separate 

 family. There are in the first place undoubted affinities in the pattern of the cheek- 

 teeth with Lepidolemur and also with the Indrisinse. Relying chiefly on the vertebral 

 column, Mivart long ago submitted that Lepiiolemur ' seems to be that genus of 

 the Lemurinae which most approximates to the Indrisinse.' In this I fully concur. . . . 

 On the other hand, Winge has insisted on the relationship of Chiromys with the 

 Indrisinse, and in my opinion he is, as usual, right here also. It will thus be possible 

 to show that these four groups, at first sight so very different from each other, because 

 each of them is specialised in a different direction, are closely related to each other, 

 and presumably had a common origin." 



There are few assemblages of mammals that present such uniform brain-features as 

 the Prosimise. The differences between the fundamental brain-types of the Lemurinse 

 and the Indrisinse are surprisingly small. The larger species of Galaginse present a type 

 of brain which is almost identical with that of the Lemurinse ; while the primitive 

 brain of Garnett's Galago and that of Loris have so many features in common that 

 the gap between the Galaginse and Lorisinse is completely bridged; and on the other 

 side the brain of Microcehus approaches near to that of Tarsitis, by far the simplest and 

 most pithecoid of all the Prosimise. 



In my recent studies (as yet unpublished) on the distribution of the visual cortex in 

 the Prosimise I have found in the genera Propithecus, Lemur, Loris, Tarsius, the 

 HapalidfP, and the Cebidse a complete series of transitional stages leading up to the 

 condition met with in the Old World Apes and Man. In this series the Hapalidse 

 come nearest to Tarsius on the one side and Loris on the other. But, in spite of the 



