1875.] PROF. W. H. FLOWER ON THE MUSK-DEER. 175 
olfactory bulb in front, dilates to form the smooth “ temporal lobe,” 
and, curving upwards and inwards, appears on the internal surface of 
the hemisphere, and passes above the corpus callosum to the anterior 
extremity of the organ. In this part of its course it 1s bounded 
above by the “ calloso-marginal sulcus”? (Huxley). This gyrus I have 
previously spoken of as “hippocampal,” because the hippocampus 
major is formed by the sulcus on its concave surface*. Above this, 
and separated from it by a very distinct horizontal sulcus, is a broad 
tract (2), extending from the front to the back of the brain, of nearly 
equal width throughout. Rather in front of the middle of this is 
External surface of brain, natural size. 
ss, superior external gyrus; m, middle external gyrus; 77, inferior external 
gyrus ; /, hippocampal gyrus; S, Sylvian fissure; O, supraorbital sulcus. 
the very insignificant Sylvian fissure (8), anterior to which a longi- 
tudinal suleus (supraorbital, O) marks off, as in the Carnivora, a 
narrow strip, the supraorbital gyrus of Leuret, which in Proteles 
appears to be the reflected commencement of the superior gyrus, 
but in the Deer looks more like a dismemberment of the inferior 
outer convolution. 
The remainder of the outer surface of the hemisphere is occupied 
by a tract, broad behind and narrow in front (s ms), extending the 
whole length of the hemisphere. In the simpler form of brains of the 
group this might be considered a single convolution ; but already in 
Moschus a longitudinal fissure towards the posterior end separates two 
tracts, which become so marked in the larger species that Leuret 
considers them two distinct gyri (s and m). However this may be, 
they always become confluent towards the anterior part of the brain. 
As regards the convolutions, then, the brain of Moschus is essen- 
tially a simplified (because small) Deer’s brain. There is, however, 
one point of importance in which it differs from the other Deers’ 
brains examined; and that is the very high position of the calloso- 
marginal sulcus, which in its posterior half becomes visible on the 
* « Anatomy of Proteles,” P. ZS. 1869, p. 479. 
