8S8 MR. R. W. PALMER ON THE 



visible only to the outside of the anterior parts of the pyriform 

 lobes. Aoioplotherium, then, was far more highly macrosmatic 

 than any living Ungulate, and not much less so than the bur- 

 rowing Aard-Vark. 



The olfactory bulbs at their widest part are together 21 mm. 

 across. The olfactory peduncles are distinct thick stalks, swelling 

 out behind into the anterior ends of the pyriform lobes. 



The olfactory tubercles are well shown as smooth circular 

 elevations placed rather further back than in Oi'ycteropiis, and 

 sufficiently prominent to be noticeable in a side view of the 

 cast. 



Between these tubercles the cast shows the coui'se of the ojytiG 

 nerves. These tunnelled the base of the skull veiy near the 

 middle line. The position of the chiasma is indicated by the 

 sinking of these tubular casts on to the general level of the bi-ain- 

 surface. Diverging outwards from the chiasma, the valleculse 

 Sylvii are distinct, marking off the globular posterior parts of the 

 pyriform lobes. Running back along the lower surface of each 

 of these lobes is the cast of the vein described as running on the 

 side of the cranium. This vessel does not seem to be cerebral, 

 but rather to collect blood from the diploe of the bones. The 

 only other feature on the pyriform lobe worthy of note is a short 

 straight fissure running along it, above the vessel just mentioned, 

 and below and parallel to the rhinal fissure. A similar fissure 

 occurs in the ]}\g and the tapir. In text-fig. 155 (p. 886) it 

 has been marked with the letter " «." 



Lateral Surface of Cerebrum. 



The olfactory bulbs having been described from below need no 

 further mention. 



The neopallium is clearly marked off from the rest of the hemi- 

 spheres by the great horizontal rhinal fssure. In text-fig. 155 

 there is a break in this fissure at about one-third of its total length 

 from the front. This break does not occur on the other side, and 

 seems to be due to dama.ge of the skull-wall. In side view the 

 rhinal fissure is seen to divide the hemisphere horizontally into 

 two equal parts, and the piimitive character of the brain is 

 emphasized by the relatively small size of the upper part (neo- 

 pallium) in comparison with the rest of the cerebrum. Its great 

 development in the higher mammals, which led to the degenera- 

 tion of the " smell-brain " and to its enwrapping by the 

 neojDallium, has scarcely begun. 



About 17 mm. from the anterior end of the hemisphere, there 

 is a vertical sulcus running into the rhinal fissure below, and 

 connected, on the right side only, by a shallow furrow with the 

 lateral sulcus. This sulcus can be no other than the orbital *. Its 



* I am using the same terms as were employed in the descriptions of the brain of 

 Ori/cteropus [4], to which I have referred, although Dr. Elliot Smith tells nie the 

 whole question of nomenclature of cerebral sulci urgentl3' needs revising in the light 

 of recent research on anatomical localization of the cerebral cortex. 



