370 DR. Cr. ELLIOT SMITH ON 



area of tlie Great Ant-eater. Tlie pyramid is now simply a branch of the main stem of 

 the central lobe. 



In size and general appearance, the cerebellum of Tamandtia is not unlike that of 

 Canis. This resemblance is also borne out to a considerable extent in the detail of most 

 parts of the organ, but the fioccular lobe presents a number of differences. The only 

 one of these which we need mention here is the fact that the projecting part of the lobe 

 is formed from the junction of the dorsal and Acntral parts of the parafiocculus, and 

 hence is not strictly homologous to the projecting part in Tamandua, which is the most 

 caudal part of the parajlocculus ventralls. 



In spite of the extraordinary difference in size in the cerebella of the Sloths, they present 

 a close structural agreement. The much smaller organ of Bradypus is slightly simpler 

 than that of Choloepus, but it will suffice to describe the latter. There are very 

 considerable differences between the appearance of the mesial sagittal sections of the 

 brain represented in figure 18 and one in the stock of the College of Surgeons. The 

 latter is larger and much more richly foliated, and, by contrast, the simplicity of the 

 brain represented in figure 18 suggests immaturity. In the latter the pyramid is a very 

 small branch of the central lobe, and forms a peculiar lip which overlaps the medulla 

 oblongata and quite liides the uvula from view. In the specimen in the College of 

 Surgeons the uvula is much larger and forms the ventro-caudal angle of the hemisphere, 

 and the pyramid is a large and independent lobule. 



The mesial section has lost the quadrilateral shai)e it has in the other Edentates we 

 have considered, being now much less angular. A large lobiis Jlocculi forms a large 

 mass on each lateral pole. This 'fioccular lobe has a similar appearance in the two 

 Sloths (figs. 11, 12). The pjarajloccuhis dorsalis consists of a large inverted V, 

 composed of deep but simple folia. The parajlocculus ventralis consists of simj)le angular 

 folia filling up the space between the limbs of the V. There is a typical anterior lobe, 

 but it presents a quadrilateral shape from being wedged between the two large fioccular 

 lobes. The area A of the central lobe resembles that of Tamandau. The area B in 

 Cholcepus is expanded to a much less extent than it is in Tamandua, and in Bradypus 

 the expansion is even less. As a result, the whole central lobe is simpler and has a more 

 distinctly quadrilateral shape, which is increased by the large fioccular lobes which 

 form its lateral boundaries. The area B is only about three times as broad as the central 

 area, with which it is in direct and iminterrupted continuity. Consequently there is 

 merely a very simple arrangement of radiating fisstires in the area B, which forms a 

 marked contrast to the feather like grouping in the Ant-eaters. The area C is also much 

 simpler, and, as a result of the lesser expansion of the area B, much broader than 

 it is in Tamandua. The pyramid is connected laterally with a group of very broad 

 folia which proceed to the dorsal parafiocculus. These folds may be regarded as part of 

 the area C. 



The posterior lobe needs no comment, as it is as constant as the anterior lobe. 



In section the cerebellum of Manis is definitely quadrilateral, but in structure it is 

 very simple and not unlike the organ in Bradyjjus, excepting that the fioccular lobe is 

 relatively smaller in the Pangolin. 



