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Show 774 MR. W. N. PARKER ON THE INDIAN TAPIR. [Dec. 19, hemispheres form marked oval elevations between the olfactory lobes and optic chiasma. Dareste1 gives a short description and diagram of the convolutions of the brain in the American Tapir; and Broca, in his admirable memoir (Anatomie comparee des circonvolutious cerebrales'2), describes the convolutions more fully, giving diagrams of an external, an internal, and a posterior view of the hemisphere; he, however, does not state to what species his description refers. Dareste's figure differs entirely from the specimen under consideration, which also does not altogether agree with Broca's account. The posterior part of each hemisphere presents three main gyri, which are much twisted, and differ considerably on opposite sides ; the outer of these is folded on itself at the posterior end, and is broader than the other two taken together. These constitute tbe four parietal convolutions of Broca. The internal and external gyri can be traced to the frontal region of the hemisphere; while the middle one, which is the simplest, stops short at about the line of junction between the anterior and middle thirds. The external gyrus is much folded in front. At about the middle of the hemispheres, the inner border of the internal gyrus passes gradually outwards, so that the posterior part of the callosal gyrus can be seen from above, thus differing from the Rhinoceros and resembling the Horse. There is a deep groove between the parietal and temporal lobes ; and this fissure (Broca's "arc inferieur de la scissure limbique") extends forwards along a curved line to the rudimentary Sylvian fissure, beneath which are seen the small convolutions of the island of Reil; these are constituted by the temporo-frontal fold, the other sub-Sylvian (temporoparietal) fold described by Broca not being present. The temporal lobe is smooth. The corpus geniculatum and corpus mamillare are well marked. The pons Varolii is rather narrow, while the crura cerebri are long. The cerebellum, though relatively larger, resembles closely that of the Horse, and presents the same irregular appearance. On viewing the hemisphere from the inside (Plate LIX. fig. 4), the calloso-marginal sulcus ("arc supcrieur de la scissure limbique" of Broca) is seen to bend down in front of the corpus callosum, as in the Rhinoceros and Horse, and does not, as in the Sheep and many other Ungulates, become superficial anteriorly. The large callosal gyrus is divided into two in its posterior part by a longitudinal fissure. Teeth.-All the milk-teeth wore in place, the dental formula being d. i. ^~3, d. c. ^Ev d.m. §-$• This corresponds with the usual statements on the subject. Behind these, traces of the developing first and second true molars could be detected in the dry skull, lying 1 "Troisieme memoire sur les circonvolutions du cerveau chez les Mammiferes," Ann. d. Sci. Nat. 4e serie, Zool. iii. 1855, p. 65. Revue d'Anthropologie, t. vii. 1878, p. 385. |
