298 DK- Gr. ELLIOT SMITH ON 



In the figures which Turner (oj). (?//•)' Gervais (ojj. cit.), and Pouchet {op. cit.) give 

 of the hrain of Dasypus we find the same ai-rangement as I have just described in my 

 specimens. 



In Tolijpentes and Xemirm we find essentially the same arrangement, hut the caudal 

 extremity of tlie posterior rhinal fi.ssure may fail in both these forms. Garrod {op. cit. 

 Proc. Zool. Soc. London, 1878) gives figures of the brain in both of these Armadillos. 



In all of the Armadillos the olfactory bulb and all the parts of the brain which are 

 intimately associated with it reach relatively enormous dimensions. Visual acuteness is 

 a matter of subsidiary importance to animals which burrow in the ground for their means 

 of subsistence, and hence the importance of a sense like that of smell, which enables 

 these animals to detect objects which they cannot see, becomes considerably enhanced. 

 Thus the macrosmatism which characterizes all mammals, except those whose pallium 

 has become sufficiently specialized to be something more than a mere sensorium, 

 becomes very much exaggerated in these burrowers, who are guided in most of their 

 pursuits mainly by olfactory impressions. 



The large olfactory bulb varies considerably in shape in the different genera of this 

 family. As the soft bulb is more liable to distortion than any other part of the brain, 

 it is safer to rely upon the evidence of cranial casts than upon the examination of actual 

 specimens when these have not been seen in the fresh state. Gervais has fortunately 

 provided us with a complete series of cranial casts of the Dasypodidae {op. cit. pi. ii.). 



From the shape of the cranial casts, as well as from all the figures of Gervais, Pouchet, 

 Turner, and Garrod, and from my own observations, it is evident that the large olfactory 

 bulbs of both species of Dasypus and also of Tohjpeutes assume a conical shape such 

 as I have already had occasion to note in the Ant-eaters, Slotlis, and Aard-varks. This 

 form of bulb is also found in the extinct Ground-Sloths Mi/lodon, Scelidotherium, and 

 probably also in Ilegatherium. It is equally found in the great extinct ArmadUlos 

 Glyptodon (in which the olfactory bulb assumes enormous proportions), and probably 

 Eutatus. In Xenurus and Tutusia the projection of the olfactory bull)s is still a 

 feature of the brain, hut it is not so developed as it is in Dasypus. There is a certain 

 amount of antero-posterior flattening of the lower part of the bulb in these forms. 

 In Chlamijdoplwrus there is a very distinct antero-posterior flattening of the bulb, just 

 as there is in the larger brain oi' tlie Pangolin {Manis). But the shape of the olfactory 

 bulb is a matter of slight importance. 



We can better appreciate the high degree of macrosmatism of the Armadillos if we 

 compare their brains with that of the little arboi-eal Ant-eater Ci/oloturus, the shape and 

 size of which is admirably shown by the figures of Tiedemann, Pouchet, and Gervais. 

 "When Ci/cloturus relinquishes a terrestrial life, such as its near relative Mi/nnecophaya 

 leads, the olfactory sense diminishes in importance, and hence we have a reduction in 

 the size of the olfactory bulbs and the rest of the apparatus pertaining to the function 



of smell. 



In the brain of tlie Armadillos the predomijiance of the sense of smell manifests itself 

 in other ways in addition to its direct effect upon the olfactory bulb. The tnberculwni 

 olfuctoriimi is uniformly very large and of relatively greater prominence than it is in the 



