344 VROT. G. ELLIOT SMITH ON THE 



shows that the separate postlateral sulcus occupies the same position in regard to the 

 skull as the mcsially l)ent end of the lateral sulcus of the other specimen. 



The brain of PerodlcUcus presents some very interesting features. 



The olfactory parts of the brain resemble the corresponding regions in Nyctlcehas. 

 The rhinal fissure resembles that already described in the latter genus. 



ho- so- fr- 



Perodictirits potto. 

 Left lateral aspect of the br<ihi. Xat. size. 



The " Sylvian fissure " is composed of the pseudosylvian and suprasylvian sulci as in 

 Lemur, but the latter furrow is not joined to the lateral sulcus as it is in Nycticebns. 

 The lateral sulcus is a simple arc surrounding the upper ends of the suprasylvian and 

 postsylvian sulci. Tlie latter is bent forward at its upper end, as often happens in 

 Lemur. There is a typical well-developed orbital sulcus and also a well-defined coronal. 



The most interesting feature of this brain, however, is an extensive transverse furrow^ 

 placed between the coronal and lateral sulci in exactly the same maniier as the sulcus 

 centralis occurs in its most primitive form in the Apes. This sulcus is obviously 

 formed by a blending of the sulcus / of the Lemurs with a sulcus such as I called x in 

 Nijclicehus ; in the genus Lemur this sulcus is probably represented Ijy the bent piece c 

 of the sulcus coronalis. The mesial surface of this hemisphere resembles that of 

 Nyctlcebus. 



]^eJdard described a brain of Perodiclicus (Proc. Zool. Soc. 1895, pp. 144 & 145) which 

 presented features essentially identical with that in the College of Surgeons. His account 

 is marred by the fact tliat he failed to recognize the lateral [liis "angular" svdcus] in 

 Nycticehus ; and most of his desci'iption of the brain of Ferodicticus, which is concerned 

 with this ])()int, is con.sequently valueless. He also quite needlessly confuses his account 

 by the misuse of tlie word " presylvian," which he applies to the sulcus which I have 

 tentatively suggested calling "central." The postsylvian sulcus bends forward as in tlie 

 last specimen. 



Ziehen (Arch. F. Psych, xxviii. p. 901) describes tlie same brain of Ferodictlcus as 

 myself; but as I had to remove the arachnoid and })ia membranes before it was 

 possible to stiuly the arrangement of the sulci, his account can hardly be regarded as 

 an accurate description. His illustration (hg. 3) bears very little resemblance to the 

 specimen in the Iloyal College of Surgeons, and is obviously adapted from one of 

 Beddard's drawings {op. clt. tig. 2i5, p. 145). Ziehen quotes tlie writings of Beddard, 

 van der Hoeven, and van Camper in reference to the brain in Lerodicticus. 



An examination of the ridges ujwn the inner walls of the cranium of a specimen of 



