FIG. 4.

The environments of subunits in three different triangulation numbers shown by an arrangement of the heads of the members of one of our groups. Only a single environment is required in the T=1 arrangement, while three and four environments are present in T=3 and T=4, respectively. Notice that a larger head (subunit) is necessary to fill the same-sized asymmetric unit for the lower triangulation numbers. The positions of the icosahedral twofold (2), fivefold (5), and threefold (3) and the quasi-sixfold (6) axes are indicated.