What is the correct syntax for /etc/network/interfaces?
Wireless will require the addition of the network you intend to connect to and any encryption details. Also, your interfaces file is a bit busy; may I suggest:
auto lo
iface lo inet loopback
auto wlan0
iface wlan0 inet static
address 192.168.1.xxx
netmask 255.255.255.0
gateway 192.168.1.1
wpa-ssid mynetwork
wpa-psk 0123456789
dns-nameservers 208.67.222.222 8.8.8.8
dns-search lan
dns-domain lan
I also suggested a backup DNS nameserver. If you are not using WPA or WPA2, the wording will be slightly different.