About `defun' in elisp manual

[Xue Fuqiao]

The GNU Emacs Lisp Reference 
Manual(http://www.gnu.org/software/emacs/manual/html_node/elisp/Defining-Functions.html#Defining-Functions)
 says:
     `defun' is the usual way to define new Lisp functions.  It defines the 
symbol NAME as a function that looks like this:
          (lambda ARGUMENT-LIST . BODY-FORMS)

Why is the lambda expression a dotted list?  As far as I'm concerned, a normal 
list is enough.

BTW, it also says:
 -- Special Form: defun name argument-list body-forms...
It doesn't mention the [DOCSTRING] argument, is it a bug?
-- 
Best regards.