44 



of the skull so broken by irregular depressions and prominent spines and protuberances. 

 The upper surface of the cranium is commonly traversed, as in the present specimen, by five 

 longitudinal bony ridges or crests, intercepting four channels : the principal crest is the me- 

 dian one, formed by the frontal and superoccipital bones ; next to this is the pair formed by 

 the parietals and paroccipitals, and the lateral pair of crests is formed by the postfrontals and 

 mastoids : the intervening depressions lodge the anterior origins of the great muscles of the 

 back and of the scapular arch. 



Hunterian. 



150. The cranium of a large Cod-fish (Gadus morrhua), consisting of the centrums 



and neural arches of the four vertebral segments of the skull. 



It shows well the cavity circumscribed by the prefrontals and vomer for the elongated 

 crura of the rhinencephalon or olfactory ganglions, and the wide anterior triangular aperture 

 of the chamber lodging the rest of the brain. 



On the right side the same numbers, on coloured tickets, are attached as in the disarticu- 

 lated specimen, No. 148. On the left side the name is attached to each bone. 



Hunterian. 



151. The cranium of a Cod-fish (Gadus morrhua), vertically and transversely bi- 



sected. The bones are numbered according to Table I. Those which enter 

 into the formation of the large cavities for the acoustic labyrinths, together 

 with the form and extent of those cavities, are well displayed ; especially the 

 deep conical excavations of the basioccipital, and the fissures or fontanelles 

 between the paroccipitals and mastoids. Presented by Prof. Owen, F.R.8. 



152. The cranium of a Cod-fish (Gadus morrhua), horizontally and longitudinally bi- 



sected. The bones are indicated by the same numbers and colours as in the 

 preceding specimen. 



The prefrontals are detached. The vomer and nasal bone are included in the same natural 

 division (neural arches) of the bones of the skull as those regarded as strictly cranial bones 

 in Human Anatomy. The cranial cavity is much contracted beneath the middle of the fron- 

 tal, and gradually expands to where it is encompassed by the vomer, nasal and prefrontals ; 

 it terminates by the junction of the nasal and prefrontals. It is thus divided by the frontal 

 or interorbital constriction into two parts; the posterior, or cranium proper, lodging the 

 epencephalon, mesencephalon and prosencephalon, whilst the anterior division is appropriated 

 to the rhinencephalon. 



Presented by Prof. Owen, F.R.S. 



