Varieties

Varieties are the arrangements of the macroscopic elements and the degree of transparency of the genera. The following points apply:

• A given cloud may bear the names of different varieties, which means that varieties are not mutually exclusive
• The exceptions to this are the varieties translucidus and opacus, both of which are mutually exclusive
• On the other hand, certain varieties may be present in several genera
• The fact that a number of varieties has been established does not imply that a specific cloud must necessarily receive the name of one or more of those varieties