Being only partial, I can't say for sure, but I think it is a fragment of echinoid spine (yes, they can be that small).
Items 1,2,3 on the plate here show examples with longitudinal striations, like yours
Of, BTW, there are foraminifera that are cylindroidal and have longitudinal lines, but those lines are protruding ribs (unlike yours).
Here's an example - http://ncfossilclub.org/~fossil/slideshow_gallery/46 (3rd & 4th photos).
I had a friend who used a digi scope to great effect with micro fossils, to the point i would say it was better than an ordinary microscope.
With it being attached to a computer and at a price that you and I can afford opens up a new and specialised world of micro fossils.
My eldest son and I once did a course on micro fossils at our local geological society and found it very interesting learning how to reduce the matrix using chemicals and heat, then sorting it out using the finest of paint brushes into a sectioned off picking dish.
Good luck with your digi scope, you have opened up a world of interest.
Please post some more images.