The two remaining figures are the two snub figures, the Snub Cube and the Snub Icosahedron.
To create a Snub Cube a mini triangle is inscribed into each face of an octahedron. Imagine the large triangle below as the face of a octahedron, the little triangle inside is the inscribed triangle.
If one of these triangles is drawn in each face of an octahedron and all of the triangles are connected to their adjacent triangles then a snub cube is formed.