[Illustration FIG. 9. A. DORSAL AND B. VENTRAL VIEW OF THE CRANIUM OF A SALMON (_Salmo salar_) from which most of the membrane bones have been removed (after PARKER). Cartilage is dotted. 1. supra-occipital. 2. epi-otic. 3. pterotic. 4. sphenotic. 5. frontal. 6. median ethmoid. 7. parietal. 8. lateral ethmoid. 9. parasphenoid. 10. vomer. 11. exoccipital. 12. opisthotic. 13. alisphenoid. 14. orbitosphenoid. 16. foramen for passage of an artery. 17. pro-otic. 18. articular surface for hyomandibular. II. VII. IX. X. foramina for the passage of cranial nerves.] The greater part of the remainder of the dorsal surface is formed of unossified cartilage which is pierced by three large vacuities or =fontanelles=. The anterior fontanelle is unpaired, and lies far forward near the anterior end of the long cartilaginous snout, the two larger posterior ones lie just in front of the supra-occipital and lead into the cranial cavity. In front of the orbit the skull widens again, and is marked by two considerable =lateral ethmoid= (fig. 9, 8) ossifications. In front of these are a pair of deep pits, the =nasal fossae=, at the base of which are a pair of foramina through which the olfactory nerves pass out; they communicate with a space, the =middle narial cavity=, seen in a longitudinal section of the skull. The long cartilaginous snout is more or less bifid in front, especially in the male (fig. 9). POSTERIOR END OF THE CRANIUM. The =foramen magnum= forms a large round hole leading into the cranial cavity, and is bounded laterally by the two =exoccipitals= and below by them, and to a very slight extent by the =basi-occipital=, the three bones together forming a concave =occipital condyle= by which the vertebral column articulates with the skull. The exoccipitals are connected laterally with a fourth pair of auditory bones, the =opisthotics=, and just meet the epi-otics dorsolaterally, while dorsally they are separated by a wide tract of unossified cartilage from the supra-occipital. The opisthotics are connected laterally with the pterotics. SIDE OF THE CRANIUM. At the posterior end is seen the =basi-occipital= in contact above with the =exoccipital=, which is pierced by a prominent foramen for the exit of the tenth nerve. In front of this lies a small foramen, sometimes double, for the ninth nerve. [Illustration FIG. 10. LATERAL VIEW OF THE CHONDROCRANIUM OF A SALMON (_Salmo salar_) (after PARKER). A few membrane bones are also shown. Cartilage is dotted.