( ( ( This type ) ( of wave ) ) ( ( travels ( along ( ( a surface ) ( that ( is ( between ( two media ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT This) (NN type)) (PP (IN of) (NP (NN wave)))) (VP (VBZ travels) (PP (IN along) (NP (NP (DT a) (NN surface)) (SBAR (WHNP (WDT that)) (S (VP (VBZ is) (PP (IN between) (NP (CD two) (NNS media))))))))) (. .)))
This type of wave travels along a surface that is between two media.
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (CD two) (NNS types)) (PP (IN of) (NP (NN surface) (NNS waves))))) (. .)))