460 PEOF. G. ELLIOT SMITH ON THE MORPHOLOGY OF THE 



densely imcked and regular layer, instead of being scattered irregularly in the thickness 

 of the wall, as is the case in the paraterminal body. In the subsequent discussion it will 

 be seen that there is little reason for hesitation in homologising the mesial portion of this 

 tbin roof the hemisphere, /. c. the part adjoining the paraterminal body, with the hippo- 

 campus or cornu Ammonis of the Mammalian brain. Hence I may be permitted in 

 anticipation to call this region by the name "hippocampus." In the roof of the 

 hemisi^here the hippocampal structure passes into continuity with another cortical area 

 which, for reasons which will appear later, I shall call " neopallium." Upon the mesial 

 surface of the hemisphere a shallow furrow, which I shall call " suleus limitans" 

 indicates the dorsal limit of the paraterminal body and the line of junction of the latter 

 with the hippocampus. 



Tlie mesial surface of the cerebral hemisphere in front of the lamina terminalis may 

 now be mapped out into areas corresponding to the hippocampus, paraterminal body, and 

 a small and ill-defined mesial portion of the corpus striatum. The accompanying sketch 



Fig. C. 



b.o. U. 



The right cerebral hemisphere oi Uphcnodon. — Semi-diagrammatic representation of its mesial aspect. Enlarged. 



of the mesial surface of the cerebral hemisphere in Sphenoclon serves to indicate in a 

 rough manner the approximate distribution of these several areas. 



In the description of the mesial structures, it has already been noted that towards its 

 upper part the lamina terminalis apj^ears to expand into a fusiform enlargement which 

 serves as a matrix for the dorsal and ventral commissures. If a coronal section through 

 the brain be made in this situation, it will be seen that the two cerebral hemispheres are 

 joined the one to the other by this matrix, or thickened lamina terminahs, which forms 

 a bridge between the two hemisjiheres. 



A comparison of the accompanying figure 7 (which passes transversely through the 

 commissures and lamina terminalis) with the previous illustration, will at once reveal the 

 identity of most of the parts of the brain exposed. Thus the relations of the " hippo- 

 campus " and " neopallium " to the paraterminal body and the corpus striatum, 

 respectively, are unchanged. In the thickened lamina terminalis will be noted in 

 addition the two cerebral commissures. The con/mlssura dorsaUs is a great U - shaped 



