. 
Literary Notices. ix 
however, be concurrent) are formed :—(a) a ventral compensatory- 
calcarine parallel to the calcarine and the dorsal limb of the postcalca- 
rine sulcus, and (4) a vertical sulcus cutting into the dorsal edge of the 
hemisphere. The latter appears to relieve the tension of the extending 
surface in a region which is obviously influenced by the proximity of 
the ‘‘apex” of the intraparietal sulcus. In some cases (e. g. Chryso- 
thrix, D. 554) this sulcus 8 may be joined to the intraparietal, but in 
most Apes it is independent of it. The two sulci a and 6 usually over- 
lap, and in most cases the intervening gyrus becomes submerged so 
that the two elements appear to form one furrow, which is the ‘‘parieto- 
occipital sulcus.” The lattter, therefore, is a complex of two (and 
often three) new elements; it makes its appearance for the first time in 
the Anthropoidea in the region between the phylogenetically old cal- 
carine and intraparietal sulci, which are the common heritage of the 
Meta- and Eutheria. This account will explain the extreme variability 
of the parieto-occipital sulci in the human brain. 
There is yet another remnant in the Primate brain of the calcarine- 
intercalary junction (which occurs in so many mammals) in the form of 
a short sulcus above and behind the splenium, which I have called 
‘‘compensatory” (instead of Broca’s misleading title ‘‘postlimbic.’’) 
The Sylvian fissure in its complete form is found only in the human 
brain, and even in Man it often imperfect. It is really a great cleft 
upon the ventro-lateral aspect of the hemisphere formed by the meet- 
ing of the peripheral opercular lips of three sulci, which are quite dis- 
tinct in origin and in their phylogenetic history. The most stable of 
these three sulci, and therefore that which takes the chief share in the 
development of the Sylvian fissure, is that called ‘‘suprasylvian” in 
most mammals. The second is an unstable sulcus analogous to the 
pseudosylvian sulcus (that which is commonly called the ‘‘Sylvian fis- 
sure”) of the Carnivora and many other mammals. And the third 
sulcus is the fronto-orbital. 
The suprasylvian sulcus is one of the most primitive and constant 
in the Mammalian series. It is the earliest neopallial sulcus to make 
its appearance on the external surface of the hemisphere in the 
course of the development of the Carnivore, Ungulate, and 
(according to the old observations of Pouchet) Edentate 
brain, synchronising in this respect with the calcarine sulcus 
on the mesial surface. Even if its identification is not alto- 
gether sure in the Marsupialia (see the accounts of TZhylacinus, 
Macropus, and Phascolomys), we know that it is a most stable sulcus in 
the Edentata, Rodentia, Carnivora, and Ungulata. In many Mam- 
mals it is joined to the less stable postsylvian (‘‘posterior suprasylvian” 
of most writers) sulcus, which we call ‘‘parallel” in the Anthroipodea. 
In the Great Anteater, however, it usually becomes separated from the 
latter and joined to a pseudosylvian sulcus to form a Sylvian fissure, not 
unlike that found in the Lemuroidea. It is significant that in the only 
case in six hemispheres of Myrmecophaga where this junction does not 
take place, it should also happen that the suprasylvian sulcus is joined 
to the postsylvian, as in the Carnivora. In Dawubentonsa the supra- 
