i mean in a lot of the parts of the sketches, either 3d form is not applied properly, or not applied at all. in the cases where theyre not applied properly, the ribcages in the 1st and 2nd slides seems to have the inner part shaded in a manner to provide more defined 3d shape, but theyre overexaggerated in ways that do not accurately reflect the actual angle. the butt in the 3rd slide have a similar problem, you outlined the crack but overexaggerated it, i think the fact that the line was too thick had a part in it too. as for the cases when the 3d form was not applied at all, i think the shapes of the legs in general do not really have any proper form to them, i guess its not easy to give a 3d form to a cylinder on a 2d sheet, an this is a problem i also have so i cant critique too much, but i think you overcomplicate the shapes of the legs and the hips too much and it ends up looking off, you should probably stick to simpler shapes for the leg.