Even in the late 1800s, getting a confused baby to sit still for a photograph forced otherwise normal parents to behave like lunatics. Sometimes it required the mother to hide herself under a carpet so it looked like their child was sitting upright of his or her own volition.
Other tactics involved the parent creeping in the background or inserting a phantom limb into the shot. In any case, these attempts at naturalistic portraits produced anything but. These children look like they're about to be kidnapped by angry poltergeists. As Sewanee: University of the South explains of this haunting practice:
19th Century photo-portraits were challenging for sitters because of the low emulsion sensitivity and consequently lengthy exposure times. In the case of children, one stress-reducing device for keeping them still was to cloak mothers and disguise them as a support on or against which the child rested.
Sometimes the floating appendages and fabric lumps were excised by picture frame borders; sometimes they weren't. You can see many more of these curiosities at the Hidden Mother: Tintypes and Cabinets Flickr pool. I'm particularly fond of the pictures that scratch out the adults' faces, thereby making the final product resemble Ringwraith Family Portrait Day at the county emporium.
Hat tip to Sven.