No Shark on OS X Lion? I can't find Shark on OS X Lion. The most recent Xcode is correctly installed, but I can only see Instruments. Has Shark been made obsolete by Instruments ?
Correct.

Shark was replaced with Instruments. There is a set of tools from Apple called CHUD that does still include Shark.

It's available here. It does require you to have a Developer Account to download. However there has been limited success in getting it to work on Lion.

It's safe to assume that Shark has bitten the dust.