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"The size of the hemispheres of the brain (A) is so small that they leave exposed the olfactory ganglion (a), the cerebellum (C), and more or less of the optic lobes (B), and they are but partially connected together by the 'fornix' and 'anterior commissure,' the great cerebral commissure known as the 'corpus callosum' being absent." — Chambers, 1881

Opossum Brain

"The size of the hemispheres of the brain (A) is so small that they leave exposed the olfactory ganglion…