Related Clues:

• Prefix with -thermic
• Skeleton opening
• Thermal opening
• Skeletal prefix
• Intro to biology?
• Outside: Pref
• ''Outer'' prefix
• Lead-in to skeleton
• Opposite of "endo-"
• Prefix with planet
• Start for skeleton
• Skeletal start?
• Start for sphere or skeleton
• ''Outside'' prefix
• Physics prefix for sphere