Still life drawing

This is my still life work using chalk drawing a shell. I first Started by drawing a rough outline of the shell then once i finished that started to add the shading and coloring . What i like about the picture is that on the main part of the shell you can see were the shell goes from  the black to the white and some of the shading on the shell.The limitations of my work is that i didn't put the shell right in front of me when i first started to draw the shell so i didn't get the right shapes and sizes of the shell. The changes that i would have make to my work is that i could have shaded with a bit more care for the top of the shell so it isn't all that grey and it has some highlights in it and to also get the right shape of the shell.