THE BHALX JX THE EDEXTATA. 



299 



Sloths and smaller Aut-eaters. The i)yriform lohe also becomes relatively much 

 laro-er, and frequently constitutes as much as half the lateral wall of the hemisphere. 

 In spite of this increase in size, the posterior part of the pyriform lobe does not form such 

 a prominent projection (" natiform eminence ") upon the base of the brain as it does in 

 the Ant-eaters. In the latter the growth of the pallium contributes toward the thrusting 

 down, as it were, of the posterior part of the pyriform lobe. 



In most of the Armadillos the pyriform lobe does not project downward to a much 

 lower level than the tuberciUnm olfactonum, and in the peculiar little distorted brain of 

 Chalmycloj)lion(s the pyriform lobe does not descend nearly as low as the ftibercultmi 

 olfacforium, which is much the most dependeat part of the hemisphere (figure 15). 



bulb. oltMt. lob, pyritorm. 



tabor:iul. olfact. 



Lateral surface of brain of Chlamtjihphorus truncaius. Enlarged 2 diam. 

 ■v. Deep groove formed b}- semicircular canals upon base of hemisphere. 



In Chlamijdophorns there is no rhinal fissure, but histological examination demonstrates 

 that the junction of pyriform lobe and pallium is placed very high upon the lateral wall, 

 so that the pyriform lobe forms more than half of this aspect of the hemisphere. It is 

 unnecessary to do more than refer to the peculiar, flattened, cake-like, sessile olfactory 

 bulb and the elliptical tuherculum olfactorinm wdiose major axis is transverse. 



The receding surface of the pyriform lol^e in Chhimndophoms is seen to even better 

 advantage in a view of the mesial surface of the hemisphere (figure 16). This, as well as 



Fig. 10. 



hippocamp. vestigia 

 Corp. oailoa. flex, liippocampi 



bulb, olfact 



psalterium 

 ventr. 



fiss. hippocampi 

 fascia dentata 



oommiss ant 



tubercul. olfact. 



area praecommisB. 



fimbria 



Mesial surface of right cerebral hemisphere of Chhiiiii/diqiJ'oriis. Enlarged 3 diam. 



.r. As in fig. 15. 



the preceding figure, shows part of the peculiar depression (a;) which we find upon the 

 ventral receding surface of the pyriform lobe, and to which Hyrtl {oj). cit.) and Pouchet 



