Black Blobs

Last night I was lying in bed reading a book. I was lying on my back, propped up a little by pillows and holding the book up to about eye level. Out of the corner of my eye, I saw something black moving. I quickly turned my head to look and found nothing. I resumed my reading. A few moments later, I saw another black object move towards the edge of my book (it was as if something passed along the edge of my bed and only a small part of it was visible as how I was holding my book blocked it). I put my book down and again saw nothing. I again resumed my reading. Several minutes passed before I saw something dark move along the left side of my bed. I thought it was my dog, but when he failed to jump up on the bed as he always does, I looked to see where it may have gone. I found nothing.