The Rostrum:
The reflected anterior portion, called the Beak or Rostrum:

• At its termination the Corpus Callosum passes backwards from its undersurface across the Posterior Margin of the Anterior Perforated space to the Hippocampus Bands
  • The Corpus Callosum Peduncles

The underside of the Corpus Callosum forms the roof of the Lateral Ventricles:
• The part of the Corpus Callosum which curves forward on each side from the Genu into the Frontal Lobe and covers the front part of the Anterior Cornu of the Lateral Ventricle is called the Forceps Anterior or Minor.

• The part which curves backwards from each side of the Splenium into the Occipital Lobe called the Forceps Posterior or Major.

The Pons

It is about an inch in length and in thickness and about an inch and a half in width. The Anterior or Ventral surface is convex from side to side.

It consists of Transverse White Fibers, which arch like a bridge across the Midline, and on either side are gathered together into a compact mass, forming the Middle Peduncles of the Cerebellum.

The Posterior or Dorsal surface forms the upper part of the floor of the Fourth Ventricle. This region is a continuation of the Reticular Formation of the Medulla Oblongata

It is called the Tegmental, as most of its constituents are continued into the Tegmentum of the Crus Cerebri.

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The Anterior or Ventral part consists of three layers of fibers:
• 1 - Superior Transverse
• 2 - Longitudinal
• 3 - Deep Transverse

The Superior Transverse Fibers
Consists of a rather thick layer on the Ventral surface of the Pons, crosses the Midline and proceeding Laterally, are collected into a large rounded bundle on each side.

This bundle, with the addition of some transverse fibers from the deeper part of the Pons, forms the Cerebellum's Middle Peduncles, of the corresponding side.

The Longitudinal Fibers
Enter the Pons below as a single mass, which forms the continuation of the Pyramids (CorticoSpinal Tract), as they divide before entering the Midbrain.

The Deep Transverse fibers
Form a thicker layer than the superficial set, and there is much Gray Matter between them.

The fibers pass from the Midline and continue to the Lateral borders of the Pons, they curve Dorsally and assist the Superficial Transverse Fibers in forming the Middle Cerebellar Peduncles.