Section 24. Figure 1, Ii., Is a More Advanced, Phase of the Same

structures. The trabeculae have met in front and sent forward a median (c.t.) and lateral parts (a.o.) to support the nasal organs. They have also flattened, out very considerably, and have sent up walls on either side of the brain to meet above it and form an incomplete roof (t.) over it. The parachordals have similarly grown up round, the hind-brain and formed a complete ring, the roof of which is indicated, by b. Further, the otic capsules are fusing with the brain-case. With certain differences of form these elements-- the trabeculae, the parachordals, and the otic capsules, are also the first formed structures of the mammalian cranium.