urgent! unfamiliar signs on boulez score

[principe7613]

hello everyone,

i'm learning a part of 'Sur Incises' from Boulez for the moment and it has two strange symbols often occuring above the staffs: a big triangle and a hook, kind of like the 'downbow'sign for stringplayers.

I need to now quite urgently what they mean. Anyone knows??

greetz,

Joost