Ellel Artists' Studios - first painting!

I painted my first picture in my new studio today! Ellel Artist's Studios is on the first floor of an ancient corn mill, 2 minutes walk from my house in Galgate. It has great light due to large windows down both sides of the room, but unfortunately those large windows also mean its a wee bit on the chilly side. I managed to work there for two hours today by putting a gas heater on either side of my desk. Ashby lay with his head so close to the heater I'm surprised he didn't singe his whiskers.
I'm currently on the lookout for other artists to share the space with. There's just two of us at the moment, but there's room for at least another two...

I'm painting some of the things from my shelf of 'stuff' - things I pick up when I'm dog walking, mainly. Sadly, moving house and country frequently in the last few years has meant that I've abandoned a lot of things, like my beaver chewed sticks from the Danube floodplain. But since moving back to the Pudding Islands I've already got a little coastal collection building up. Beaches are the best place to find interesting things. When I'm home for Christmas in Fife I'll pick up my skull collection. I left it in my old bedroom while I was living in Vienna. My parents will probably be grateful because they use the room for guests.

Does anyone know what kind of shell the bigger one is?