mystery clamp Help

Since 2001, over 90,000 cyclist's have joined Cycling Forums to discuss topics from general cycling to equipment, training, racing and travel or vacation destinations (especially in europe during the tour de france). We also feature an great deals in our online store, 100's of articles, classifieds and product reviews.

I have a specialized allez sport, I was cleaning the bike last night and there is a black plastic clamp type thing sliding around between the bottom bracket and f derailleur. I cant for the life figure out its purpose. Anyone with this model of bike that can take a look and let me know.
Thanks

Is it like what is pictured in this old post:

http://www.cyclingforums.com/showthread.php?p=3310319&highlight=tooth#post3310319

That's it, now it becomes so obvious
thank you