The infra-orbital foramen is generally narrow, and the tympanic bulla hollow.
This primitive condition occurs only in the Odontornithes, Ratitae and Tinami; in all others this notch becomes converted into a foramen ischiadicum, through which pass the big stems of the ischiadic nerves and most of the bloodvessels of the hind-limb.
The femur often possesses a well visible pneumatic foramen on the median side of the proximal end of its shaft.
From its occurrence in so many of the lower vertebrates, the entepicondylar foramen of the humerus, as it is called, is regarded by Dr E.
In the region of the neck lateral strands pass through the transverse canal of the cervical vertebrae; but from the thoracic region onwards, where the cardiac branch to the heart is given off, each strand is double and the basal ganglia are successively connected with the next by a branch which runs ventrally over the capitulum of the rib, and by another which passes directly through the foramen or space formed between capitulum and tuberculum.
In the more extended sense, the Anomaluroidea are diagnosed as follows: In the skull the infra-orbital foramen (or canal) is large, the lachrymal foramen placed high up, and no transverse canal; while the malleus and incus of the internal ear are fused.
The heart is practically quadrilocular, the right and left halves being completely partitioned, except for a small communication, the foramen Panizzae, between the right and left aortae where these cross each other on leaving their respective ventricles.
It is therefore very probable that the authors quoted in (2) were mistaken in their identification of the elements at the base of the foramen magnum.
V, Foramen of exit Fr, Frontal.
The posterior, so-called processus Zygomaticus is very variable; in many Galli it encloses a foramen by distally joining the orbital process.