WOEPHOLOGT OF THE BRAIX IN THE MAMMALIA. 3 tO 



13"5 iwm. long, and is so oblique that its lower end (measured in projection) is 10 mm. 

 further forward than its upper end. The natiform eminence of the pyriform lobe is 

 a very narrow conical projection on the base of the hemisphere. As in the genus 

 Lemvr, and unlike the condition found in the Lorisiate, the orbital excavation extends 

 back t(j the Sylvian fissure. 



The thi]i, vertically-placed, leaf-like olfactory bulb resembles that of the Lorisinije. 



The rhinal fissure is almost wholly obliterated. 



The Sylvian fissure, which is constituted like that of Galago and the Lorisin;r, 

 extends obliquely upward and backward on to the dorsal surface, and divides the latter 

 into a broadly expanded posterior part (which extends as a thin leaf over the corpora 

 quadriyemina and the anterior part of the cerebellum) and a narrow tapering anterior 

 part. 



There is a typically triradiate group of calcarine, retrocalcarine, and paracalcarine 

 sulci, the greater portions of which are situated in the mesencephalic fossa on the low er 

 surface of the caudal region of the hemis])here. There are no other sulci. 



The notes on the brain in Ilicrocebus and Chirogale in the oft-quoted memoirs of 

 Gcrvais, Beddard, and Ziehen add little more. Beddard records the preseuce of a very 

 small lateral (his "angular") sulcus (Proc. Zool. Soc. 1895, p. 117). 



The BiiAiN ix the Ixdrisix^e. 



Practically all that is known of the structure of the brain in this subfamily is contained 

 in that part of the ' Ilistoire Naturelle des Mammiferes' of MM. Alph. Milne-Edwards 

 and Alfr. Grandidier which forms volume vi. of Alfr. Grandidier's great ' Histoire 

 de Madagascar.' The other memoirs which refer to the brain of any of the Indrisime — 

 viz., those of Zuckerkandl and Cluulzinski — either add nothing new or are borrowed from 

 Milne-Edwards's great work. Flatau and Jacobsohn derive their account of the brain of 

 Indris from Chudzinski, to whom thev accord all the credit for a research whicli is 

 either wholly or for the greater pait oljviously a reproduction of the account given Ijy 

 Milne-Edwards. 



Gcrvais describes moulds of the cranial cavity iu the Indrisina?. lie dojs not seem, 

 however, to have exercised sufficient care iu the study of the impressions which correspond 

 to the cerebral sulci. Eor in the Lemurs, and especially in the genera Propitheciis and 

 Indris, it is possible to accurately map out all the sulci on the outer surface of the cerebral 

 hemisphere, if a critical examination be made of the prominent bony ridges on the inner 

 face of the cranium or of the furrows [)roJuced by these ridges on a mould of the cranial 

 cavity. 



I have examined a considerable series of crania of the Indrisime in the British Museum 

 and in the Collection at the Royal College of Surgeons, and have thus been able to gain 

 a much more accurate conception of the jjlau of the sulci than that conveyed by the 

 lithographs which illustrate the ' Histoire de Madagascar.' 



17r. Eorsyth Major lent me an excellent skull of an adult male Fropithectts diudona, 



