Let's get oriented by looking at some snow crystals from Nakaya, 1954.
These snow crystals were collected at ground level, rather than at cirrus levels. A habit diagram shows how the various ice crystal shapes depend on temperature and water vapor supply. Most of this diagram does not include temperatures typical of cirrus crystals.
From snow observations, Magono and Lee have derived a snow crystal classification scheme, as seen in part 1 and part 2. The images below are from their classification scheme.
It is still not known if the Magono and Lee classification is appropriate for cirrus crystals. Our opinion is that cirrus clouds contain only a subset of the crystals shown by Magono and Lee, and that the crystals studied by Magono and Lee were probably much larger than 'typical' cirrus crystals.
