Great! Thanks, John, I needed the boost here...I was too overwhelmed by the possible magnitude of possibilities in "Tipulidae sense lato" to take a stab at it initially. But emboldened by your comment, I looked at the MND and the 1967 "Crane Flies of California" by C. P. Alexander [PDF here (26 MB)]. And, as you say, this is definitely genus Ptychoptera...the wing venation is quite distinctive, and I *think* I can barely make out in my photos the basal appendage to the halter (or "prehalter") mentioned in the key to families in the MND.

Alexander (1967) lists 6 species in CA...though it lacks a key, and just gives original publication references and partial locality records. The six species are:

    byersi...........original description on pp. 104-105 here;
    lenis.............original description on pg. 206 here;
    minor...........original description on pp. 3-4 here;
    monoensis.....original description on pp. 20-21 here;
    sculleni.........original description on pp. 39-41 here;
    townesi.........original description on pp. 37-38 here.

P. townesi is the only species in Alexander (1967) with a collection record from San Mateo County, although lenis and minor have records listed from nearby San Francisco County. The other 3 species seemed further removed geographically, based on records given in Alexander (1967)...which may be a misleading criteria, as such records are by their nature often incomplete.

From my initial reading of the descriptions there seems to be a lot of overlap. I should read them again more carefully when I get a chance, but P. minor seems perhaps the best fit to me so far...I like this part of its description: "Abdominal tergites black, segments three to nine with the lateral margins broadly reddish".

The descriptions linked to above are mostly based on male specimens...but I found an image of P. townesi that appears to be a female.

There may simply not be enough to go on in these images to separate what appear to be fairly subtle differences among the species here (at least outside of terminalia).