20 
MR. W. K. PARKER OK THE STRUCTURE AND 
possible that the foremost part of the paired trabeculae may have helped to thicken 
the bulbous part. 
At a short distance from the nasal wall the fore part of the orbitosphenoid is shown 
in section ; but further forwards (see Plate 5, fig. 1, o.s.) that wing is continuous with 
the nasal wail. Over these parts the frontal shows itself twice, above, where it lies 
over the flattish hemispheres (CH), and laterally, where the orbital plate protects the 
orbitosphenoid over the eye-ball (e.). 
The nasal channels are almost reduced to two sub-oval naso-palatine canals, for 
here the skin covering the vomer (v.) lies very near the skin covering the halves of the 
hard palate. 
Four bony sections are seen here ; the two small upper pieces are the hinder forks of 
the vomer ( v .), the outer and larger plates are the palatine bones (pci.), which extend 
round the passage, above and below. Below, these bones soon meet at the mid-line, 
like the maxillaries, carrying on the hard palate (see Plate 2, fig. 6, mx., pa.); above, 
they nearly touch the forks of the vomer. Under each eye-ball there is a bony section, 
flattish and upturned externally ; this is the jugal (j.). Nearer the mid-line the 
large high dentary (cl.) is seen, and inside its lower part Meckel’s cartilage ( mJc.). 
13 th Section (Plate 4, fig. 1).—This partial figure shows a very long part of the 
frontal bone (f.) and a larger amount of orbitosplienoidal cartilage (o.s.), confluent, 
here, with the outside of the narrowing nasal labyrinth, but at a distance from its own 
root, the presphenoid. The median cartilage is still the perpendicular ethmoid (p.e.), 
and its shape here is very instructive ; the extension of the cartilage below the nasal 
labyrinth is due to the addition, right and left, of a wedge-shaped tract—the cornu 
trabeculae to each side of the bulbous, crested intertrabecula.* 
The cavity of the nasal labyrinth is now reduced to three small recesses, the outer 
nearly obsolete ; and the folds of the middle turbinal (m.tb.) are confluent with both 
wall and floor, and look inwards and upwards. Here the top of the intertrabecula has 
lost the crest (crista galli); the cartilage here, behind the cribriform plate, is lowering 
towards the presphenoidal region. 
In the last section the upper part of the mucous membrane lining the naso-palatine 
canals almost rested upon the lower so as to divide them imperfectly. Here these 
folds are more separated in the middle, and the canal (n.jJ.c.) is single, shallow in the 
middle and deeper at each end. Outside this common canal tire pterygoid bone (pg-) 
is seen merely hooking round the passage in a crescentic form. 
The high coronoid region of the mandible (cl.) is here cut across, and Meckel’s 
cartilage (mk.) is seen lying on the inturned lower edge; the jugal (j.) still comes 
into section under the eye-socket. 
14 th Section (Plate 4, fig. 2).—This is through the widest part of the orbito- 
* This part is explained by what is seen in the early chondrocranium of the Turtle and the Crocodile 
(see ‘Challenger Reports,’ Zoology, vol. 1, plate 5; and Trans. Zool. Soc., vol. 11, plate 64, fig. 5; 
and plate 65, figs. 2, 3, 7). 
