The internal surfaces of the canal are unmarked either by muscle scars or Foramina.
"Two New Pelycosaurs from the Lower Permian of Oklahoma"
Richard C. Fox
The length of the incisive Foramina in meridionalis, expressed as a percentage of the total length of the skull, is usually greater than in chiapensis.
"Records of Harvest Mice, Reithrodontomys, from Central America, with Description of a New Subspecies from Nicaragua"
Sydney Anderson J. Knox Jones
The head of the alligator is broader and the snout less prolonged, and the canine teeth of the under jaw, instead of being received into Foramina in the upper, as in the crocodile, fit into furrows on each side of it.
"Sketches of the Natural History of Ceylon"
J. Emerson Tennent