Penryn is a collective name for revised Conroe uarch and 45nm process. Conroe was such a name, too, but it was also a codename of specific core; Allendale, Kentsfield and Clovertown are analogic to Wolfdale and Yorkfield.
Also Yorkfield is not a native quad core - native means there are four core on single silicon piece (like AMD's K10). Kentsfield, CLovertown and Yorkfield consist of two silicon pieces on one PCB under one IHS.