One difference between Byblis liniflora and B. filifolia is that B. liniflora is self compatable, seed can be obtained by selfing the flowers. B. filifolia cannot be "selfed" for seed production. B. filifolia is usually larger than B. liniflora at maturity, but some plants of B. filifolia can be quite small, so size is not a good identification tool, except on large (greater than 17cm/ 8") forms of B. filifolia. B. liniflora does not produce any distinct pulvini, and B. filifolia does, on pollinated peduncles.
The only Byblis that I know I have grown are Byblis liniflora, B. 'Goliath', and a Byblis that was either B. gigantea or B. lamellata. The last two species do not have circinate vernation. According to Wikipedia B. lamellata has deeply ridged seed that make it distinct.
I believe this genus is very complex, with a great number of unknown morphological & genetic features that have not been adequately observed and described yet.
Hi Cindy, Byblis gigantea is the southern form that occurs around Perth. It is a smaller plant that readily divides from the root systems. B. lamellata is the northen form that is much more robust "tree like" and doesn't divide from the roots as easy. I have a copy of the renaming and new Byblis descriptions somewhere if you would like a copy, PM me. Cheers Phill