From the ArcaMax Publishing, Gardening Newsletter:
http://www.arcamax.com/news/gardening/s-2563-775272
Catfacing is when tomato bottoms are deformed. Too hot or cold temperatures during flowering cause poor pollination, which causes this condition. Older varieties are more susceptible. Fruits are edible, but to avoid it next year grow modern varieties.
This news arrived on: 07/19/2008