. On the anatomy of vertebrates [electronic resource] . and 123, hind part is embraced by the 6 callosal convolution, ib. These fibres are shown at x, fig. 4, pi. vii. lxx., which gives a view of the hippo-campal fold from the ventricular or lateral side, as part of a thin stratum of medul-lary fibres arching oyer the hippocampus major, and continued therefrom into theinternal wall of the ventricle, p. 95. 2 If we could examine the brains of Dinosauria or Dicynodontia, the actual gap inthe series of cerebral structures might be better filled. 3 Prom this point in the lowest (Lyenceph
. On the anatomy of vertebrates [electronic resource] . and 123, hind part is embraced by the 6 callosal convolution, ib. These fibres are shown at x, fig. 4, pi. vii. lxx., which gives a view of the hippo-campal fold from the ventricular or lateral side, as part of a thin stratum of medul-lary fibres arching oyer the hippocampus major, and continued therefrom into theinternal wall of the ventricle, p. 95. 2 If we could examine the brains of Dinosauria or Dicynodontia, the actual gap inthe series of cerebral structures might be better filled. 3 Prom this point in the lowest (Lyencephalous) mammals, as in the embryo ofthe highest, the growth of the great supraventricular body of transverse commissuralfibres forming the corpus callosum begins : Anterior fibres of the taenia hippo-campi continued into the anterior lobes of the hemispheres. lxx. p. 95, pi. 4 and 6, o; and pi. vii. fig. 4, x. 4 The part marked b in the Echidna has become the part marked n in Man. Pis,xxxvi. and xxxviii. of XLm. 102 ANATOMY OF VERTEBRATES. 70. Lateral ventricle, Echidna. Such are the essential characters of the Mammalian e prosen-cephalon. The chief modifications of the Mammalian brain, asabove characterised, will next be noticed in thedifferent leading groups of the class. A. Lyencephala. In the Ornitliorliynchus,the brain, figs. 52 and 69, is to the weight of thebody as 1 to 130 ; the hemispheres are triangu-lar, depressed, the broader posterior part over-lapping the optic lobes, and reaching to thecerebellum. With the exception of the hippo-campal fissure, fig. 69, 4, and the depressionlodging the rhinencephalic crus, the surface isunbroken or smooth, with a few vascular im-pressions diverging from the fore part. Themedulla oblongata is broad and depressed; thecorpora pyramidalia, fig. 51, a, are in very low relief; the corporaolivaria, a, expand as they advance ; they are crossed anteriorlyby the i corpora trapezoidea, b, which are large ; the 6 pons, c, isnarrow :
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