206 C. W. M. POYNTER AND J. J. KEEGAN 
Fig. 7 A view ofthe tentoral surface, showing some variations of the sulcus 
collateralis and the fissura rhinalis. In A the sulcus collateralis and the fissura 
rhinalis are independent. B shows the fissura rhinalis still distinct but connected 
with an additional element, marked ‘A’; this secondary element is brought into 
existence by some growth process which results in the obliteration of the central 
portion of the fissura rhinalis. C shows the anterior connection gone, the poste- 
rior end carried farther back and the antero-lateral element still present. D is 
another stage in advance and in E a union. has occurred between the fissura 
rhinalis and the sulcus collateralis, the antero-lateral element is better developed 
and only a superficial groove marks the position of the internal portion of the 
fissura rhinalis. 
