e floor in some species large
anterior basal ganglia or _corpora striata_ are found
(Miklucho-Maclay, _Beitrage z. vergl. Neurol._, 1870; Edinger, _Arch.
mikr. Anat._ Bd. lviii., 1901, p. 661, "Cerebellum"). The Teleostean
Fish are chiefly remarkable for the great development of the optic
lobes and suppression of the olfactory apparatus. The pallium is
non-nervous, and the optic tracts merely cross one another instead of
forming a commissure. A process of the cerebellum called _valvula
cerebelli_ projects into the cavity of each optic lobe (Rabl.
Ruckhard, _Arch. Anat. u. Phys_., 1898, p. 345 [Pallium]; Haller,
_Morph. Jahrb._ Bd. xxvi., 1898, p. 632 [Histology and Bibliography]).
The brain of the Dipnoi, or mud fish, shows no very important
developments, except that the anterior pineal organ or paraphysis is
large (Saunders, _Ann. and Mag. Nat. Hist._ ser. 6, vol. iii., 1889,
p. 157; Burkhardt, _Centralnervensystem v. Protopterus_, Berlin,
1892).

[Illustration: From _Cat. R.C.S. England_.

FIG. 17.--Section of the Brain of Porbeagle Shark (_Lamna_).]

In the Amphibia the brain is of a low type, the most marked advances
on that of the fish being that the anterior commissure is divided into
a dorsal and ventral part, of which the ventral is the true anterior
commissure of higher vertebrates, while the dorsal is a hippocampal
commissure and coincides in its appearance with the presence of a
small mass of cells in the outer layer of the median wall of the
pallium, which is probably the first indication of a hippocampal
cortex or cortex of any kind (Osborn, _Journ. Morph._ vol. ii., 1889,
p. 51).

[Illustration: From _Cat. R.C.S. England_.

Fig. 18.--Section of Brain of Turtle (_Chelone_).]

In the Reptilia the medulla has a marked flexure with a ventral
convexity, and an undoubted cerebral cortex for the first time makes
its appearance. The mesial wall of the cerebral hemisphere is divided
into a large dorsal hippocampal area (fig. 18, _Hip._) and a smaller
ventral olfactory tubercle. Between these two a narrow area of
ganglionic matter runs forward from the side of the _lamina
terminalis_ and is known as the paraterminal or precommissural area
(Elliot Smith, _Journ. Anat. and Phys._ vol. xxxii. p. 411). To the
upper lateral part of the hemisphere Elliot Smith has given the name
of _neopallium_, while the lower lateral part, imperfectly sep