378 PKOF. G. ELLIOT SMITH ON THE 



Propithccits, and Acaliis. The writer lias apparently overlooked Plower's footnote 

 (quoted above) which clearly shows that a posterior cornu is not necessary to the 

 existence of the calcar. The latter must be present in tlie Indrisinse (because a calcarine 

 sidcus occurs in this subfamily as it does in the I,emurinffi) even though the posterior 

 cornu may be absent. For this is obviously what the author means to imply. His other 

 statements regarding the posterior cornu and calcar avis (on p. 205) are contradictory 

 and their meaning is not altogether clear. 



The only other writers (so far as I am aware) to refer to the posterior cornu in the 

 Lemurs are Flatau and Jacobsohn (' Handbuch,' p. 189) ; and as they have obviously not 

 read any of the literature quoted above (excepting Burmeister's remark concerning 

 Tars/'iift) they dismiss this, the most crucial feature of the Prosimian brain, in that 

 casual manner, which is unfortunately the rule rather than the exception in their barren 

 and misleading work. Thus they dispose of the whole question in the case of Lemnr 

 macaco in the words : — " Der Seitenventrikel ist bei den Halbaffen von gleicher Eeschaf- 

 fenheit, wie bei den wahren Affen und audi von den gleiclien Gebilden begrenzt " 

 (p. 1S9), as though there were no problem to be settled. Moreover it will lie shown that 

 this observation is misleading, if not quite erroneous. The only other Prosimian brain 

 which the authors examined was one which they label " Stenops gracilis," but wliich 

 obviously belongs to " Nycticebus tardigracbi.sy Now although the interesting problem 

 as to the existence or absence of the posterior cornu in this genus had been definitely raised 

 and loft unsettled {vide supra) by Plower (whose numerous and important contributions to 

 the Comparative Anatomy of the mammalian brain these writers of a text-l)ook on this 

 su])ject almost wholly ignore), Platan and Jacobsohn merely state (in tlie paragraph 

 corresponding to that quoted above regarding Lemur) : — " Die iibrigen Vorhaltnisse am 

 Gehirn des Stenops sind so iihnlich denen am Gehirne des Maki, da^-s cine l)esondere 

 Eesprechung unnotig erscheint" (p. 199). But, as in the case of Lemur, they give 

 tables of measurements, among which figures " Abstand der vorderen Spitze des 

 Vorderhornes vom hinteren Pol des Hinterhornes " (pp. 199 and 189) *. 



Ziehen, Beddard, and all other recent writers do not even so much as refer to the 

 subject. 



After carefully examining the specimens concerning which the above-([uoted state- 

 ments of Plower's were made, I felt convinced that an undoubted patent posterior 

 cornu exists in the genus Lemur. I subsequently made dissections of the brains of 

 Nycticebus, Microcebiis, Tarsius, and two other specimens of Lemur, all of which had 

 been in preservative solutions for long periods ; and the results seemed to confirm my 

 earlier conviction. But recently I examined the fresh brain of a Lemur f ulcus, and, to 

 my great surprise, found mo trace of any patent posterior cornu. Since then I have been 

 unable to find any posterior cornu in three other fresh brains of various species of Lemur 

 and a fresli brain of Nycticebus. In view of these unquestionable facts, and of the 



• This reference to a " Hinterborn " is, liowevor, meaningless, for tbey use the term in referring to the brain of 

 all mammals. 



