I was moving pretty fast on this one, maybe a bit too fast. I drew the whole ear very similar to the guide on the left, the I wiped it down to very faint lines. This prep drawing had a lot of mistakes so I re-drew all the lines again with more measuring, then once again wiped it all down to make the lines very light. I also added a bit of charcoal to the paper to tone it a bit so that any of my guide lines would be hidden easier. Lastly I used a generals charcoal pencil to draw the finishing lines.
At least two major errors, circled above, and a few smaller errors in accuracy. Like the far left line of the ear, and the top most line.
I found another great use of the sanguine lead that I was using today in life drawing, unfortunately I had worn down the only piece I had to a very small nub, so it was very hard to get a point on it or hold it. This is why my traced line is so bad.