104 ANATOMY OF VERTEBRATES. 



The term ' cranium ' might well be applied to the four neural 

 arches collectively, figs. 76, 83; but would exclude some bones 

 called ' cranial,' and include some called ' facial,' in Human 

 Anatomy. In a side view of the naturally connected bones of 

 those arches, such as is shown in the Carp, fig. 83, the upper 

 part of the cranium is formed by the neural spines called super- 

 occipital 3, parietal 7, frontal n, and nasal 15; the lower part 

 by the centrums called basioccipital i, basisphenoid 5, presphe- 

 noid 9, and vomer 13: the side-walls by the neurapophyses called 

 exoccipital 2, alisphenoid 6, orbitosphenoid 10, and prefrontal 14. 

 Between 2 and 6 is intercalated the petrosal 16 : between the 

 fore part of 9 and 10 is the ' interorbital 18,' which is an inconstant 

 ossification in fishes. The outstanding or transverse processes 

 are the paroccipital 4, the mastoid 8, and the postfrontal 12. 



83 



Cram urn of a Carp. 



In the Carp the parietals meet and unite upon the vertex by a 

 c sagittal ' suture : in most osseous fishes, as in the Cod and Perch, 

 figs. 76, 77, they are separated by the junction of the superocci- 

 pital, 3, with the very large frontals, n, n. At the base of the 

 skull may be seen, in the Perch, fig. 84, the basioccipital i, the 

 articular processes of the exoccipitals 2, and the spine-shaped end 

 of the superoccipital 3. The paroccipital 4, is separated below 

 from the exoccipital by the petrosal 16. The basi-presphenoid, 5 

 and 9, carries forward the bodies of the vertebra? to the vomer 13, 

 which is expanded and dentigerous anteriorly, as the bodies of 

 the cervical vertebra? support teeth in the Deirodon (p. 57). The 

 alisphenoids 6, the orbitosphenoids 10, and the prefrontals 14, are 

 attached to the sides of the basal elements ; more externally are 

 seen the frontal 11, postfrontal 12, mastoid 8, and paroccipital 4. 

 On the left side are shown the palatine 20, the entopterygoid 



