Dalton's Crawling Update

Dalton started crawling about 2 weeks ago but before that he was rolling from place to place he is now crawling from the living room down the hall to Whitney's room (where all of the extra toys are) and from the living room through the kitchen and to my bedroom door. He will push up on all fours then collapse down and move his little legs and just one arm I think its the left arm and he has also started trying to crawl flat on his back schooching his legs and back only a few feet at a time. He has also started rolling on his side and propping up on one arm so the sitting up on his own is soon to come.