294 



DE. G. ELLIOT SMITH ON 



Myrmecoi^haga. In both representatives of the Myrmecopliacjidce the rhiual fissure is 

 nearer the base_.of the In-ain than it is in Orijcteropus, so that in a view of the ventral 

 surface practically the whole of the fissure is visible (tig. 9). 



Fis. 9. 



fiss. rhinal. ' 

 loc. perforat 

 tract, opt. 



Corp. mammill.- 

 nerv.V. 

 trapezium 



bulb, olfact. 



..ped. olfact. 

 -lob. pyrifonn. 

 tuber, olfact. 

 ■ nerv. II. 

 tuber, tract, olfact. 



infundib. 

 crus cerebri 



pons Varoi. 



.|;>-~ parafloec. 



.. ^flocculus 



nerv. VIII. 

 pyramid. 



Ventral surface of brain of Tamandua. Nat. size. 



It follows from the above remarks that the shape of the pyriform lobe is very different 

 in the American Ant-eaters, and esjiecially the Great Ant-eater, from that which we 

 have found in the African Aard-vark. Thus in 3Iyrmecoplictga, and to a less degree in 

 Tamandua, there is a very distinct flexure in the pyriform lobe which is wanting in 

 Orycferopus. The pyriform lobe is besides relatively smaller in the American forms. 

 In these brains also the anterior limit of the pyriform lobe upon the mesial surface 

 of the brain is more distinct, because the peculiar hijapocampal tubercle which we 

 found in Orycteroptts is lacking in the Ilyrmecophagidce, and the hippocampal fissure, as 

 a consequence, extends much lower (fig. 10). As a result of the flexure of the pyriform 

 lobe in Ilyrmecopliaga, the vallecula Sylvii is deepened and a number of deep clefts or 

 puckerings indent the surface of the pyriform lobe in this region. They are probably 

 mere mechanical results of the bending (fig. 7). 



In Tamandua the tuhercuhmi olfactorium presents the same quadrilateral shape which 

 we noted in Ilyrmecophaga. The olfactory bulb is relatively smaller than it is in the 

 larger brains, and its peduncle is not so prominent because its dorsal surface is completely 

 hidden by the anterior pole of the hemisphere. 



My knowledge of tlie conformation of the brain in the small arboreal Ant-eater 

 Cycloturus has, in the al)sence of any material, been derived mainly from the imperfect 

 notes and illustrations which Pouchet (op. cit.) has contributed, and the even less 

 complete observations of Tiedemann {op. cit.) and Gervais {op. cit.). It is not clear 

 from Pouchet's work whether any rhinal fisstire is present in the small arboreal Ant-eater. 

 He says in the text that the brain of Cycloturus (which he calls Dionyx) is smooth, 

 and he does not represent a rhinal fissure in his figure. But since he does not represent 



