This one is very curved at the top. It's the biggest one and is starting to get soft enough so that I can feel it give a little when I squeeze it, sort of the texture of a zucchini.
Most of them are shaped more like this. This one is still hard.
They look small in the picture, but they're probably about 10 inches long. I thought it might even be a gourd, but they're pretty heavy and fleshy. Aren't gourds hollow?
Who knows what it is?
Update: I've been searching on the internet and think I might have found it - Green Striped Cushaw Squash. If so, it's really considered a pumpkin and can weigh 10-20 lbs. Oops, I probably shouldn't have put it on a trellis.