mammary ridge

n.
  1. A bandlike thickening of ectoderm in the embryo extending from just below the axilla to the inguinal region and giving rise to the mammary glands.mammary fold milk line
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.