See Javadoc

A Pyramid is a four sided object with a square base and triangle sides. All four sides are equal.

In jME to create a Pyramid simply supply the width and the height of the pyramid. The width is the width at the base, and height is from the base to the peak.

Pyramid p = new Pyramid("Pyramid", 10, 10);
rootNode.attachChild(p);

<Octahedron|User's Guide|Quad>