Testing Google IPs just got a whole lot more interesting.
The range 184.108.40.206-220.127.116.11 is from China and all those IPs have the proper reverse DNS crawl-203-208-60-nnn.googlebot.com.
Why 18.104.22.168 was skipped, I have no clue.
Here's the whole block allocated to GoogleCN
inetnum: 22.214.171.124 - 126.96.36.199
status: ALLOCATED PORTABLE
changed: firstname.lastname@example.org 20110412
descr: FM China Network
changed: email@example.com 20060612
This appears to be legit so do what you must to make sure you're not bouncing Googlebot!
Now I have to punch a hole in my Great Firewall of China which, due to both email and web abuse, is in an actual iptables firewall, not a soft firewall like everything else. Hat tip to new member Igal Zeifman [webmasterworld.com] for pointing me at this new development.