The basi-sphenoid soon coalesces with the pre-sphenoid, which is developed from a distinct point of ossification between the rings of bone forming, in the foetus, the optic foramina. The descending pterygoid processes are appendages of the haemal arch of the nasal vertebra. They extend backwards, maintaining their typical connection with the palate bones, and confluent with the basi-sphenoid, that the upper jaw may be immovably bound to the base of the skull. In most birds the upper beak moves slightly upwards when the mouth is opened ; and we find, in connection with this freedom of movement, that the palate bones and pterygoid processes are unattached to the prolonged cylindrical basi-sphenoid. An incorrect idea of the typical vomer would be formed from the examination of that bone in the human skeleton only; in the codfish it is evidently a repetition of the cranial centra. Of elongated form, superiorly concave, thicker anteriorly than posteriorly, it supports the neurapo-physes, which form the sides of the last neural arch in the head. In the turtle it assumes somewhat of the ploughshare form commonly seen in man: in the ostrich it is a thin concave plate of bone, which receives the prolonged extremity of the presphenoid. In the human foetus it somewhat resembles that which is seen in the ostrich ; but it is compressed laterally into a thin vertical plate, which assists in the formation of the septum nasi, with the descending plate of the ethmoid, and with the vertical nasal cartilage.