THE BRAIN IN TH]'] EDENTATA. 307 



and obtusely pointed, without a trace of tlie reflected rostrum." In my specimen of 

 Cholrepits, as well as in the representative of Brmhjpus, the anterior extremity of the 

 corpus callosum is fuller and not pointed as seems to have been the case in Plower's 

 specimen. There is, as Flower remarks, no reflected rostrum or genu in Cholcepus, but 

 in my specimen of Brad>jpuii there is a most decided genu, for the plump anterior 

 extremity of the short corjius callosum j^resents a considerable curve in the ventral 

 direction. 



The shape of the psalterium and its relation to the corpus callosum in the Sloths 

 recall that peculiar reversion to a simpler type of cor2)us callosum which we have 

 previoiisly met in Nyctophilus and other Bats *. The difference is a considerable increase 

 in the size of the corpus callosum in the Bj-adypodidce. 



Ill the Sloths the anterior commissure is relatively smaller than it is in either 

 Ilyrmecophaga or Orycteropus, probably because the pyriform lobe is relatively smaller 

 in the former. 



In three schemes which I have prepared to illustrate the vai-iations in the hii^pocampus 

 in the three American families {vide infra, tig. 23), the shapes of the commissures are 

 clearly demonstrated and their marked contrast shown more forcibly than any description 

 can picture them. 



In the Armadillos we meet with yet another type of dorsal commissure which markedly 

 contrasts with both of the types — those of the Bradypodidie and Myrmecophagid(e — whicli 

 we have just described. A representative of this type is seen in Dasypus viUosus. Here 

 we find a dorsal commissure composed of two limbs — corpus callosum and psalterium — 

 of approximately the same size, but of different shai^es. Both of these limbs are 

 placed very obliquely and in contact one with the other for the greater part of their 

 extent, only a very small part of the extreme anterior end of the corjous callosum being 

 separated by any interval from the psalterium. As a result, there is practically no septum 

 lucidum, in the sense in which that term is applied in human anatomy. 



The anterior extremity of the diminutive corpus callosum is pointed and depressed. 

 The psalterium and corpus callosum each consist of a club-shaped mass of fibres of 

 approximately the same size. The thick end of the club in the case of the psalterium 

 consists of the cut edge of a vertical wall of crossing fibres, which are placed above the 

 anterior commissure. This mass is the pjsalteriiim ventrale. At its upj^er extremity it 

 tapers to the handle of the club, ^nliich is composed of the psalterium dorsale. This is 

 short and is inclined slightly backward, and becomes continuous with the thick end of 

 the club-shaped mass of the corpus callosum, which is placed upon the dorsal aspect of 

 the psalterium dorsale. The corpus callosum is extremely oblique, and rapidly tapers to 

 a point anteriorly aud below. A very slight interval is left between the anterior 

 extremity of the corpus callosuui and t\\e pjsalteriuin ventrale. 



In Turner's description tiud figure of the brain of Dasypus sexcinctus t there is no 

 indication of any distinction between Wxe ptsalteriuni dorsale and ventrale, and the whole 



* Cf. this Vol. p. 47. 



t Turner. «p. cil., 'JouriKil of Anatomy and Physiology,' vol. i. 



