I have a form similar to this:

Code HTML4Strict:
<form id="test">
    <input type="text" class="amount" value="300">
    <input type="text" class="amount" value="100">
   <input type="submit" name="submit" value="Show Total">

... and the following jQuery to calculate the input values total:

Code JavaScript:
var total = 0;
        total += $(this).val();

The problem is that,upon submit, I do not get a calculated total of all values. Instead, it just echo's out all the individual values.
What am I doing wrong here?