Species
(Section 2.2.2.2)Most cloud genera are subdivided into species due to peculiarities in the shape of clouds and differences in their internal structure.
A cloud belonging to a certain genus may bear the name of one species only; this means that the species are mutually exclusive. On the other hand, certain species may be common to several genera. When none of the definitions of the species are relevant to a genus, no species is indicated.
