THE COD. 91 



In the Whiting the anterior anal fin extends in front of the caudal 

 region, so that most of its interspinous bones are unconnected with the 

 vertebrse and lie free amongst the muscles. 



19. The fin-rays, attached, in the case of the dorsal and 

 anal fins, at their proximal ends to the interspinous bones, 

 and forming the actual skeleton of the fins ; each is a deli- 

 cate, rod-like bone, transversely jointed and flexible at its 

 distal end (" soft fin-rays "). In the caudal fin the fin-rays 

 come into direct relation with the hypural bone and the 

 posterior neural and haemal spines. 



In the Codfish there are 13 rays to the first dorsal fin, 16 to 19 to 

 the second, 17—19 to the third, 18—19 to the first anal, and 17— 18 to 

 the second. The formula for the fin rays is therefore, D. 13 | 16 — 19 | 

 17 — 19- A. 18—19 I 17—19- In the Haddock the formula is D. 

 14 — 16 I 20—24 I 19—21. A. 24 — 25 I 21—22 ; and in the Whiting 

 D. 13—14 I 20—23 I 20—21. A. 33-35 I 22—24. 



VII. In the brain-case make out the following points : — 



20. The single concave occipital condyle, for articu- 

 lation with the centrum of the atlas : it is the hinder face 

 of the basi-occipital bone (Fig. 29, b.d), which forms the 

 posterior part of the base of the skull, ending in front by a 

 thin jagged edge. 



21. The foramen magnum or occipital foramen, a 

 large aperture immediately above the occipital condyle, for 

 the passage of the spinal cord into the brain. 



22. The ex-occipitals {e.o), two irregular bones forming 

 the lateral boundaries of the foramen magnum and articu- 

 lating below with the dorsolateral edges of the basi-occipital. 

 Each ex-occipital is perforated by an aperture for the exit of 

 the vagus nerve, and presents on its posterior border an arti- 

 cular facet for the corresponding surface already seen on the 

 neural arch of the atlas (§ 9). 



23. The supra-occipital {s.o), a large bone bounding 



