slow worm skeleton

Observation - slow worm skeleton - UK and Ireland. Description: I found this minute skeleton in the garden which must be either slow worm or grass snake: just a little wedge shaped head and long spine in 'ox bow' shape. Is there any way of distinguishing one from the other at this stage - like size at hatching? I hav

I found this minute skeleton in the garden which must be either slow worm or grass snake: just a little wedge shaped head and long spine in 'ox bow' shape. Is there any way of distinguishing one from the other at this stage - like size at hatching? I have a compost heap but haven't found any eggs or shed skin as I would expect if there were grass snakes around, but have never seen slow worms here either. We do have lots of newts...