get() return nothing

Hello, there,
I wrote a loop to check the dimension of all the .txt dataframes:> ls()
?[1] "actualpca.table" "b4galnt2"??????? "b4galnt2.txt"??? "data"
?[5] "galnt4"????????? "galnt4.txt"????? "galnt5"????????? "galnt5.txt"
?[9] "galnt6"????????? "galnt6.txt"????? "glyco"?????????? "glyco.txt"
[13] "i"?????????????? "mtscaled"??????? "newsig.table"??? "nicepca"
[17] "pca"???????????? "sig.txt"???????? "st3gal3"???????? "st3gal3.txt"
[21] "st3gal5"???????? "st3gal5.txt"???? "st6gal1"???????? "st6gal1.txt"

for(i in ls(pattern="txt")){dim(get(i))}

If I check individual ones, they are ok:

dim(get("galnt4.txt"))

[1] 8 3

could anyone help me to figure out why it did not work with a loop?
Thanks a lot!

Ace