This has me completely stumped.

I brought home some eelgrass and sea lettuce from White Rock beach for my hermits. This hairy spine-like thingy came along with it.

Just over 3 cm. long, broken off at the wide end. Still wet.

The "spine" looks like a fish spine, but even under the microscope, I can't see segmentation. It may be all one piece. The hairs, under the microscope, look like human hair, on the fine side, more like a baby's hair. I can't see any sign of individual cells, like the hairy seaweeds have. Each hair sprouts from a row of pores around the stem; two to three deep, then a space, then a gray line, then the white gap before the next circle.

The stem is smooth and white on the outside, grainy in the centre. Wet or dry, it is flexible.

Dry, and combed with a soft paint brush. Very soft to the touch.

Detail of the wide end, showing the rows of hairs.

I have pored through my books and the web. I've looked at weird worms, hairy plants,horsetails, seaweeds, legs of assorted critters . . . I can't find anything like it. I don't know where to look next.

Help!

*UPDATE:
A commenter on Facebook suggested the smell test with a burning piece. I tried that. It smells like burnt hair or feathers.