Select last row of a table without an ID with jQuery

Select last row of a table without an ID with jQuery

I have using some scrape technology that will read the last row of a table
using jQuery.
The table itself has no ID so I can only select it using the following code:
$('table[width="100%"]'); // select the table on the page with a width of
100%
I've tried the following line to get the last row but it returns
'undefined':-
$('table[width="100%"] tr:last'); // returns 'undefined'
$('table[width="100%"] tr') // returns the first row as expected
Can anyone suggest any advice why it would be doing this..