Step 13:

Picture of
Spine Ridges (cc color)

Thread a long piece (a little over 1 1/3 times the length of the body and head) of cc yarn on to the yarn needle.  Sew a running stitch from the tip of the tail to the head, just behind the eyes, making the line as straight down the back as possible.  Just leave a length of yarn between the body and the head.