Cool! - I might have made the humerus a little thicker. Cheers!

Nice work! It's good to take the time to analyze the proportions. Now comes the difficult part of applying it in your figurative work XD. You'll constantly be working on proportions :) It's one thing to have memorized them, and another to get them right in your drawings. You might forget them every now and then, so you'll be refering back to the proportion chart. - I've heard that when the old masters talked about proportion, they didn't only talk about proportions, but also about symmetry. Proportion AND symmetry. This could be something to be aware of when you draw. It's difficult to get right, and I have a lot of practicing to do there, but if you look carefully at your drawings, you'll notice that the arms aren't perfect mirror images of themselves. The skeleton isn't symmetrical. To help with getting the symmetry right, it helps to draw a vertical line, cutting through the center of the skeleton; a symmetry line. By comparing the distances to the centerline you can assure symmetry. This vertical line will also help keep allignments in check, and with making sure that the figure is standing straight. In the drawing to the left of image one, the ribcage and pelvis don't line up, suggesting a crooked spine. This is getting picky, but focusing on accuracy has it's place. You might want to practice trying to draw a perfectly vertical line on a page. Do your best guess, compare with the edges of the paper, which you consider to be perfect verticals. Then measure the distance of the ends of line to the paper edge. If the measurements aren't the same, the line isn't vertical. Make adjustments. Also, place the ruler against the line to see if the line is straight. I've found it benficial to do the same with a horizontal line. Try to get these two to run through the center of the page (forming a plus +), and you'll get some extra practice in dividing things in halves (check if it's a true split by measuring with a ruler.) As you do this exercise, you'll find what your tendencies are. If I try to split a vertical distance in half, for example, I tend to make the lower part longer than the upper. This is probably the reason why I make the legs too long in my figure drawings. When doing figure drawings, one thing that could help with getting the symmetry is to draw the corresponding parts together. So for example, when you've drawn the right upper arm, you go to the left upper arm, trying to make sure they're the same length in space. I hope this helps :)

Nice! - Your circles are a bit off. I think I would recommend drawing spheres as a warm-up for a short time. Check their accuaracy with a compass or a ruler. Also try fitting them into squares, that you might divide into 4ths or with diagonals. After having done this a little, your awareness of circle and square accuracy will have improved. You tend to make the circles too wide, and this error spreads into the rest of the figure. Improving the accuracy of your circles and boxes will improve proportions overall in your drawings. In my drawings I tend to make the legs too long. When I've done the exercise of trying to split a distance in half (I draw a vertical line, then decide on a top and bottom, then mark halfway), I've noticed that I tend to put the halfway mark too high. Working on this has improved the leg proportions in my drawings. Hope this helps :)

These are a little hard to see but they're fairly decent. Watch your proportions. On some of them I notice stuff like the rib cage being too large or the femur being to short.

Nice! - Remember that a cranial unit is a sphere. You seem to have given it an ovoid form. Cheers!