Symmetrical (Wave-formed) ripple marks
_________________________________________
Asymmetrical (Current) ripple marks
(direction of current: right to left <<< )
Wave-formed ripple result from the to-and-fro motion of waves and have a symmetrical profile.
Current ripple marks form in response to water or wind currents flowing in one direction and have asymmetric profiles.
The asymmetric profiles allow geologists to determine paleocurrent directions, in other words, which direction the wind or water was flowing from when the cross beds were deposited. This is possible due to the fact the longer side of the ripple always faces the upstream direction."
http://thisoldearth.net/Geology_Online-1_Subchapters.cfm?Chapter=5&Row=3
Asymmetrical (Current) ripple marks
(direction of current: right to left <<< )