372 PEOF. G. ELLIDT SMITH OX THE 



Avords, there is formed a calcar avis of such i^reat iivoportions as to closely resemble in 

 shape and size that of the smaller Apes. This calcar is larger than that of the other 

 Prosimia', although the condition found in the Galaginae nearly approaches it. 



It is noteworthy that in Ziehen's memoir on tlie Lemur's brain this calcarine sulcus — 

 the only true sulcus found in the brain— is entirely ignored, although reference is made 

 to a large number of spurious sulci. If this significant sulcus had really been absent, as 

 Ziehen's account would lead one to suppose, this would have placed the bi-ain of Tarsias 

 in a category quite apart from that of all the other Lemuroidea (and in fact all Primates), 

 instead of adding vet another convincing testimonv to tlie close Prosimian affinities 

 of Tarsiiis. 



About midway between the calcarine sulcus and the ventral border of the hemisphere 

 there is a very deep irregular notch extending backward on to the caudal margin of the 

 liemisphere. When the brain is in situ in the skull, this deep depression is occupied by 

 the bony case of the strongly projecting fiocculai' lobe of the cerebellum. 



Ziehen* represents two separate depressions in this situation: one on the mesial 

 surface, which he refers to as /3, and the other he calls " die Einbuchtung der untereii 

 Contours des TemiJoro-occipitallappeus." They are obviously both parts of the one 

 lloccular fossa. Although when describiua; the Tarsius-brain Ziehen inclined to the 

 \ie\\ that the sulcus /5 is merely a depression caused by a bony projection, yet in the 

 same memoir we find this writer discussing which of two sulci in the hemisphere of 

 Xijcticehus (p. 906) represents the "sulcus /3 in Tarsiiis" \ Then he adds, " Am 

 Avahi'scheinlichsten ist mir, dass /3 wenigstens z. Theil audi dem Yereinigungspunkt von 

 p, o, luul TT [the calcarine group of sulci] entspricht." If this suggestion is correct, 

 Ziehen's drawing (tig. 2, p. 900) is very misleading and erroneous, for the relationship of 

 his sulcus /3 to the floccular fossa (his " Einbuchtung") is very different to that of tlie 

 true calcarine sulcus. 



Just below the retrocalcarine sulcus there is in one of my specimens a shallow 

 horizontal furrow, which crosses on to the caudal margin of the hemisphere. As it is 

 very shallow and lodges a branch of the posterior occipital artery, it is possible that it is 

 caused by the latter. In neither hemisj^here of ray second specimen is there any such 

 sulcus. 



The narrow cleft between the optic chiasina and the tuberculum olfactorium, which 

 contains the representative of the locus j^t'iforatus of other mammalian brains, is 

 prolonged transversely outward across the pyriform lobe as a vallecula Sylvii. Opposite 

 the outer end of the latter a furrow extends outward (upward) and slightly forward 

 across the orbital excavation of the hemisphere, which it divides into two approximately 

 equal parts. It occujjies the situation of and probably represents the Lemurid Sylvian 

 fissure. It does not extend so far up as tlic dorsal lip of the orbital excavation, so that 

 it is not visible on the dorsal surface, although an indentation of the margin (tig. 13) 

 indicates its situation. A comparison with the condition found in Microcehm shows that 

 this must represent the Lemurid Sylvian or suprasylvian sulcus. When we remember 

 that the area which is usually called " orbital surface " lies wholly in front of the 



* Arch. f. Psvchiat. xxviii. ISHG. p. OUU. 



