A ventral view of the cartilaginous cranium shows much the same points as the side view. The basisphenoid appears on the surface immediately in front of the basi-occipital.

The Skull with membrane bones.

The dorsal surface. The greater part of the dorsal surface in front of the supra-occipital is overlaid by a pair of large rough frontals (figs. 9, A, 5, and 10, 5). They cover the posterior fontanelles and stretch over from the sphenotic to the lateral ethmoid, forming a roof for the orbit. They meet in the middle line behind, but in front are separated by a narrow tract of unossified cartilage, and are overlapped by the median ethmoid (figs. 9, A, 6, and 11, 6). At the sides of the supra-occipital behind the frontals are a pair of small parietals (figs. 9, A, 7, and 11, 7).

[a]Fig. 11. Lateral view of the skull of a Salmon] (Salmo salar)
(after [a]Parker]). Cartilage is dotted.

1. supra-occipital.19. maxillae
2. epi-otic.20. premaxillae.
3. pterotic.21. articular.
4. sphenotic.22. angular.
5. frontal.23. dentary.
6. median ethmoid.24. hyomandibular.
7. parietal.25. symplectic.
8. nasal.26. epi-hyal.
9. lachrymal.27. cerato-hyal.
10. suborbital.28. hypo-hyal.
11. supra-orbital.29. glosso-hyal.
12. cartilaginous sclerotic.30. opercular.
13. ossification in sclerotic.31. sub-opercular.
14. meso-pterygoid.32. infra-opercular.
15. meta-pterygoid.33. pre-opercular.
16. palatine.34. supratemporal
17. jugal.35. branchiostegal rays.
18. quadrate.36. basi-branchiostegal.

In a ventral view the cranium is seen to be chiefly covered by two large membrane bones, the parasphenoid (fig. 9, B, 9) behind, the vomer in front. A view of the posterior end differs from that of the cartilaginous cranium only in the fact that the end of the parasphenoid appears lying ventral to the basi-occipital.

The lateral view differs very markedly from that of the cartilaginous cranium, there being a great development of membrane bone in connection with the jaws and branchial apparatus. Lying dorsally are seen the median ethmoid, frontal, parietal, and supra-occipital as before. Lying external to the middle of the median ethmoid is seen the small nasal (fig. 11, 8), and below the hinder part is the lachrymal. The lachrymal (fig. 11, 9) forms the first of a series of seven small bones which surround the orbit forming the orbital ring. Of these the one lying immediately in the mid-ventral line of the orbit is the suborbital, while the one lying in the mid-dorsal line and attached to the frontal is the supra-orbital (fig. 11, 11). The orbit has a cartilaginous sclerotic in which are two small ossifications (fig. 11, 13) laterally placed.

Bones of the upper jaw.