Connected my iphone 5 (with latest iOS7 software) to my Dell PC. In iTunes, I CANNOT DELETE any songs!

I have connected my iphone 5 (with latest iOS7 software) to my Dell PC. Opened up itunes, clicked 'On this iphone' and brought up the list of songs on my device. I CANNOT DELETE any songs! So frustrating, I want to mass delete a bunch of songs. Please help. The right answer is not 'swipe right to left' on your device to delete songs one by one. I want to delete about a hundred songs at once.

Thanks,

Joe