Beattie. — Oil the Anatomy uf the Red Cod. 78 



bone is intercalated between two adjoining dermal-fin rays, its 

 hatchet-shaped dorsal portion seeming to abut against or 

 articulate with, on the one hand, the posterior edge of the base 

 ■of a fin-ray, and, on the other hand, with the anterior edge of 

 the base of the fin-ray immediately behind. Closer examina- 

 tion of a freshly-prepared skeleton, however, shows that the 

 interspinous bone articulates not with two adjoining dermal- 

 fin rays, but with two adjoining nodules of cartilage (a.c, fig. 

 10). These nodules are perfectly distinct, and lie in the hollow 

 of the saddle-shaped base of the dermal- fin rays. Each is 

 pear-shaped, and is in length about one-twentieth of that of 

 the dermal-fin ray, and in breadth about one-third of that of 

 the base of the dermal-fin ray. This cartilage seems to me to 

 correspond with that found in the Eibbon Fish (Begalecus 

 argciiteiis) by Professor T. J. Parker, and to which he refers as 

 follows : " . . . . an ovoidal cartilage on wdiich is 

 perched . . . a dermal-fin ray. I have not met with cartil- 

 ages of this kind in any fish wdiich has come under my notice, 

 and can find no account of any such in the works at my dis- 

 posal. I regard them as representing a second or distal series 

 of radials orpterygiophores, the interspinous bones forming the 

 proximal series." 



Following the last undoubted caudal vertebra is a fan- 

 shaped bone — the hypural. This bone, together with foiu' 

 others (two dorsal and two ventral), give the symmetrical 

 appearance to the Teleostean tail. These bones, at first sight, 

 appear to be flattened neural and haemal spines ; but they are 

 attached, three to the last undoubted caudal vertebra and one 

 to the hypural, by ligament only. 



A very obvious cartilaginous nodule against which the 

 posterior v^rds of the prffimaxilla and maxilla abut is found in 

 Lotelln, and is identical with that found in Gadus. Curiously 

 enough, as Professor Parker has pointed out, no mention is 

 made of this in the leading authorities. 



There is at the posterior part of the cranium on eacli side 

 of the basioccipital a rather large aperture partly closed by a 

 very thin lamina of bone. This aperture is bounded dorsally 

 by the exoccipital, laterally and internally by the basioccipital, 

 laterally and externally by the opisthotic, and ventrally by the 

 basioccipital and opisthotic. This aperture opens into the 

 auditory capsule, and will be referred to in the description of 

 the air-bladder and auditory organ as the auditory fontanelle. 



The cartilaginous parts of the cranium are situated in the 

 ethmoid and auditory regions. 



In the ethmoid region there is a median cartilage lying 

 below the mesethmoid and above the vomer throughout the 

 full length of the latter bone. This cartilage sends off pro- 

 cesses into vacuities in the mesethmoid. About its centre it 



