THE BRAIN IN THE EDENTATA. 297 



of pallium : in other words, an increasing disproportion between the sizes of the pallium 

 and the pyriform lobe. It is such inequalities in the rate of growth of these funda- 

 mentally distinct cortical areas that give rise in all probability to the rhinal fissure. 



In Chlami/dophonis there is uo rhinal fissure whatever, but in all the other Dasypodidae 

 there are small anterior and generally also posterior rhinal fissures, w^hich are separated 

 by a varying interval in different genera. 



In Tatusia noremcincta, two specimens of which I have had the opportunity of ex- 

 amining, we see the arrangement of these fissures in a typical manner. A short anterior 

 rhinal fissure begins in the cleft between the olfactory bulb and the apex of the pallium, 

 and extends horizontally backward for less than a third of the length of the hemisphere. 

 A posterior rhinal fissure, which is very shallow, extends from just below the middle 

 of the posterior border of the hemisphere and passes forward for less than a third of 

 the length of the hemisphere. In the figure which Pouchet gives of a young Tatusia 

 {op. cit. pi. vi. fig. 1), these fissures are only indicated very faintly. As both of the 

 specimens which I examined were distorted, I have modified this figure of Pouchet so 

 as to indicate the features present in my specimens (fig. 13). 



Fig. 13. 



fiss. rhinal. post. 



fiss. rhinal. ant. o 



...paraflooc. 



bulb, olfact. ! 



tubercul. olfact. \ 



lob. pyriform. 



Scheme of lateral surface of brain of Tatuf'ui [Hha. 



In the pallium, just above the wide gap between the anterior and the posterior 

 rhinal fissures, we find a short oblique fissure which may be distinguished as 0. 



Fig. U. 



S 

 ■ \ fiss. rhinal. post. 



fiss. rhinal. ant. 



,j)arafloco. 



bulb, olfact. ; ; '"''• pyriform. flocculus 



: : tuBer. tract, olfact. 



. ,. ,'f . tubercul. olfact. 

 tract, olfact. 



Lateral surface of brain of U'lsiqu's si.rcinrttia. Nat. size. 



In Dasypus sea'cinctus (fig. 14) and Basi/pm vUIosks we find practically the same 

 arrangement of the rhinal fissures, with the difi'ereace that the more extensive posterior 

 rhinal fissure enters into uninterrupted continuity with the pallial fissure /3. 



