The proportions of the four ossifications are approximately the same.
In Teleostei and bony Ganoids, a considerably greater number of ossifications occur in the cartilage.
There are three centres of ossifications for each vertebra, two in the arch and one in the centrum.
In Polypterus the pectoral fin (fig. 18, B) shows three ossifications in the basal part of the fin—pro-, meso- and metapterygium.
In the Amphibia the ossifications in the cartilage are comparatively few.
In front of the orbit the skull widens again, and is marked by two considerable lateral ethmoid (fig. 9, 8) ossifications.
The hyoid arch has a number of ossifications in it and is closely connected with the mandibular arch.
Lateral ethmoids are developed, and there are ossifications in the sphenoidal region which vary in different forms.
There is a large parasphenoid, but there are no ossifications in the basisphenoidal, presphenoidal, and alisphenoidal regions.
The lower jaw or mandible remains partly cartilaginous, while its ossifications include two membrane bones and one cartilage bone.