THE NORTHERN RIBBON-FISH. 3 
We may consider the skull in detail under the several headings of (1) the 
cranium ; (2) the jaws, and (3) their suspensorial apparatus ; (4) the hyoid and 
branchial arches ; and (5) the opercular series. 
The Cranum. (Plate I., Figs. 1,3, 4. I1., Figs. 5, 6.) 
The supra-occipital is a cone-shaped bone, with oval base and rounded apex. 
The base forms part of the inner wall of the brain-case, and is traversed by 
large cavities which open inwards. The posterior and lateral margins of the base 
are articulated by slight cartilaginous intervention with the frontal and with the 
Fig. 1. Ixvernat Vinw oF CRANIUM. 
ep., epiotic; ex.-oc., ex-occipital; fr., frontal; op., prootic ; s.oc., supra- 
occipital (in this specimen, smaller and less prominent than in the other) ; 
sp., Sphenotic; t.c., tegmen cranii; v., ViI., foramen for the fifth and seventh 
nerves. 
epiotic, the latter bone providing a shelf-like ridge for its reception. The 
parietal articulates with the lateral margin of the base, also, just external to the 
frontal and under cover of the epiotic. Anteriorly the bone articulates with the 
cartilaginous tegmen cranii. Thus the supra-occipital is here, as in Regalecus, 
displaced from its proper connection with the exoccipitals, owing to the great 
development of the epiotics, but it is a larger and much higher bone. The rounded 
apex forms the posterior dorsal angle of the skull. 
The ex-occipitals are irregular in shape, but each may be described as 
consisting of a body, a wing, and an anterior process. The body, in each case, 
presents a notch which together form the foramen magnum, below which the two 
bones meet in the middle line, and above which they are only separated by a 
median cartilage. The body of the bone forms the dorso-lateral facet of the occipital 
condyle, below which is a foramen for the vagus nerve. The wing is a shell-like 
expansion which lies over the epiotic, and helps to form the pit for the lodgment of 
the post-temporal. Its lower border articulates with the lower portion of the 
pterotic. The anterior process articulates with the prootic. Internally it is 
excavated to form, together with the prootic and the epiotic, a pit which 
probably lodges the horizontal semi-circular canal. 
Basi-occipital.—As has already been pointed out, this bone does not enter into 
the formation of the foramen magnum. It presents a surface posteriorly which 
joins with the ex-occipitals in forming the occipital condyle. Below it sends down 
