THE BRAIN m THE EDENTATA, 327 



the hijopocampal fissure, and upon reaching the dorsal part of the hemisphere it does 

 not hend forward but continues its course as far as the dorso-posterior corner of the 

 hemisphere, where it ceases just before reaching the dorsal surface of the hemisphere. 

 In the right hemisphere this sulcus just crosses the upper edge to reach the cranial 

 surface. In his description of the brain of Cholcepus Hoffmanni Turner says * that this 

 sulcus, which he does not name, extends on to the cranial surface above. Flower f does 

 not represent any sulcus corresjjondiog to a! in his specimen of Cholcepus dklacti/lus. 



In my young specimen of Bradijpus trldactylHS there is a very well-developed sulcus a', 

 which presents an arrangement exactly analogous to that which Turner has described in 

 Chola-pus Hoffmanni. It begins below just in front of the rhinal fissure, and ascends 

 vertically ; in its upward course it is placed upon the caudal rather than ujion the mesial 

 aspect of the hemisphere, as was the case in Cholaqjus, and crosses the postero-superior 

 border of the hemisphere at a distance of about 3 mm. from the interhemisplieral cleft ; 

 it, or more strictly a sulcus y with Avhich it is in uninterrupted communication, extends 

 forward for a distance of 10 mm. on the dorsal or cranial surface of the hemisphere (left). 

 On the right hemisphere of this brain the sulcus 7, w'hich is in continuity with a', is 

 much shorter, while in the brain of Bradi/pKS in the College of Surgeons this sulcus y 

 extends for more than half the length of the hemisphere. 



In the brain of Cholapus a longitudinal sulcus divides tlie area of j)alliuni which lies 

 above the corpus callosum into two horizontal bands, of which the lower is slightly the 

 narrower. In my specimen of Cholapus dldactylus this sulcus, which we may call a", 

 begins slightly in front of the corpus callosum and terminates close to the ujiper 

 extremity of the sulcus a' by bifvircating so as to form a short vertical sulcus parallel 

 to 05'. In Flower's specimen of the same species the sulcus a'' begins slightly further 

 forward and extends considerably further backward before it ends simply without 

 bifu.rcating. In Turner's specimen of Hoffmann's Sloth this sulcus, which Turner calls 

 by Krueg's designation of '' splenialls" begins far forward and with a bifurcated 

 extremity ; posteriorly it bends downward into a direction parallel to the sulcus a', and, 

 according to Tu.rner, is " apparently continuous with the hippocampal fissure." Sucli 

 apparent junctions between the hippocamjial and other fissures are of absolutely no 

 importance, because the ftssiu-a hipjJOCciDipl is quite sul generis, and of a nature entireh- 

 diff'erent from all other fissures or sulci. 



In my specimen of Bradypus the sulcus a" begins far forward in a bifurcated extremity 

 in much the same manner as it does in Turner's specimen of Cholcepus Hoffmanni. In 

 the right hemisphere it ends simply at the posterior extremity, but in the left hemisphere 

 there is a slight bifurcation, and in addition a small independent vertical sulcus midway 

 between the adjacent extremities of a and a". 



In all the specimens representing the brains of Sloths we find a well-defined family 

 type in the mode of disposition of the mesial surface of the jmllium. 



Among aU the Armadillos we find some arrangement of sulci analogous to the series a, 

 except in Chlamydop)horus, which, like Ci/cloturus, has a smooth pallium. 



* Turner, op. cit., Journal of Anat. & Physiol, vol. xxv. p. 122. f Flower, 021. cit., Phil. Trans. 1865, fig. 5. 



45* 



