I have the following HTML:
Try:
$('#mydiv').find('.myclass');
JS Fiddle demo.
Or:
$('.myclass','#mydiv');
JS Fiddle demo.
Or:
$('#mydiv .myclass');
JS Fiddle demo.
References:
Good to learn from the find() documentation:
The .find() and .children() methods are similar, except that the latter only travels a single level down the DOM tree.