Heads are thin, usually fewer leaves than the mexican fan palm, and should have lots of old leaves attached.
Leaves evergreen, palm shaped, grey-green in color, 12 or so feet long counting the petiole, the fan part about 5 to 6' diameter. Leaf segments dividing about half way to the base of the leaf. Leaf edges usually showing lots of white fibers, hence the filifera, more so than W. robusta and the tips of the leaflets weeping downward.
Trunks are very stout, thick, and almost cylindrical to the ground, sort of like the Chilean Palm and very unlike the Mexican Fan Palm. 2-3 feet wide if the skirt has been removed.
Washingtonia robusta has a much thinner stem, more leaves in the head and less "thread" from the leaf margins, though that is hard to see at 40-50' in the air. Picture below shows 2 robustas (tall and far right and the filifera on the left.
On the three way corner of Chico/Auburn/Modesto only 3 left, better hurry
There are several on Morrissey Drive interplanted with Washingtonia robusta.
From the highway towards Soquel Dr. 462, 439, 428, 433, 331, 230