 Hmmm, might be an abalone shell.
( Hmmm ( , ( ( might ( be ( an ( abalone shell ) ) ) ) . ) ) )
(ROOT (S (ADVP (RB Hmmm)) (, ,) (VP (MD might) (VP (VB be) (NP (DT an) (JJ abalone) (NN shell)))) (. .)))
After thinking for a second, I believe that could be an abalone shell.
( ( After ( thinking ( for ( a second ) ) ) ) ( , ( I ( ( believe ( that ( could ( be ( an ( abalone shell ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN After) (S (VP (VBG thinking) (PP (IN for) (NP (DT a) (NN second)))))) (, ,) (NP (PRP I)) (VP (VBP believe) (SBAR (IN that) (S (VP (MD could) (VP (VB be) (NP (DT an) (JJ abalone) (NN shell))))))) (. .)))