Halliday & Matthiessen (1999: 27):
There are many examples of cryptotypes in this sense, both as classes and as systems (i.e., cryptoclasses and cryptosystems), in our ideational semantics. For example:
process types: doing & happening/ sensing/ saying/ being & having
transitivity model: ergative/ transitive
projections: locutions/ ideas
expansions: elaboration/ extension/ enhancement
number: plural/ non-plural; singular/ non-singular