The first one is the newer "screwdriver" tailcone. The shadow from the horizontal stabilizer is blocking a complete view. The screwdriver cone was installed on new aircraft produced after a certain date, and was retrofitted to older models. It has a 1 or 2 percent better fuel burn result than the older DC-9 style tailcone, which is pictured in the second image.
Why didn't Continental modify its 66 MD80's with the scredriver tail?? All of them have the old-style one. I
guess it does not matter now, since the MD80's are
very slowly being phased out in favor of 737-800/900
aircraft but I'm just curious. Continental went to
great lengths to revamp its aircraft interiors so why
not change the tails too? Too expensive probably.