832 PROFESSOR DAVID HEPBURN ON 
whose lower end will be seen resting upon the fronto-parietal operculum of the insula, 
and I have marked it by this name in fig. 1. In this respect my drawing and its 
interpretation are more in agreement with Muriz’s* account of the sea-lion, although 
in his drawing the fissure of Rolando is represented as much more extensive than it 
appears to be in the Weddell seal. 
TURNER describes the cruciate fissure of the elephant seal as seen from the front and 
not from the norma verticalis, and states that ‘‘a large sigmoid gyrus was bent around 
its outer end.” ‘To some extent this description would apply to the Weddell seal, 
although in the latter the cruciate fissure was visible from the norma verticalis, but it 
was much more effectively seen from the norma frontalis, while its outer end was 
blocked by an arched gyrus (fig. 1). 
I could not find any satisfactory evidence of a homologue for the external parieto- 
occipital fissure, and therefore no fixed indication of a limit between the parietal and 
occipital lobes of the cerebrum on its lateral aspect, or between the occipital and 
tempero-sphenoidal lobes on the same aspect, for the reason that these areas were freely 
connected with each other by annectant gyri. 
The Convolutions on the Lateral Surface. 
The frontal lobe having been delimited in the manner described, its convolutions 
resolved themselves into a pre-central (ascending frontal) ; the frontal contribution to 
the opercula of the insula ; and two or three short convolutions running forwards from 
the pre-central convolutions towards the sulcus cruciatus. 
The elongation of these short convolutions in a forward, 7.e. frontal, direction would 
have the effect of forcing the sulcus cruciatus forwards and downwards towards the roof 
of the orbit, and would thus bring the cruciate fissure into position as a kind of 
boundary line between the frontal and orbital aspects of the frontal lobe. It appears 
to me that the blunt frontal end of the brain of the Weddell seal is due in some 
measure to the presence of convolutions, which in the human brain would be found in 
relation to the roof of the orbit. Further, in the human brain there may sometimes be 
seen a fissure which runs transversely from the pallial fissure across the frontal lobe 
and close above the orbital margin of the hemisphere. In my opinion this is a fissure 
which may fairly be regarded as corresponding with the sulcus cruciatus. 
In the figure given by Murir, and already referred to several times, there is, on the 
frontal side of the fissure which is marked “ Rolando,” a convolution named in three 
places as the antero-parietal convolution (AP); and I cannot but think that this was an 
unfortunate term to introduce at such a place so long as the fissure of Rolando is 
accepted as a boundary line between the frontal and parietal lobes of the highly 
elaborated brain of man. 
From the fissure of Rolando (fig. 1), and beginning at a point about its middle, a 
well-marked fissure ran backwards towards the occipital end of the hemisphere. This 
* Morin, loc. cit., pl. Ixxviii., fig. 40. 
