34 FAMILY OF THE ASTEROLF.PIS. 





af the body, the anterior dorsal opposite the ventrals, and 

 the posterior dorsal opposite the anal fin. The fin-rays of 

 ;he various members of the family, and such of their spinous 

 processes as have been detected, were hollow tubular bones ; 

 or rather, like the larger pieces in the framework of the pla- 

 coids, they were cartilaginous within, and covered externally 

 by a thin osseous crust or shell, which alone survives ; and 

 to this peculiarity they owe their family name, Celacanth, 

 or "hollow-spine." The internal hollow, i. e., cartilaginous 

 centre, was, however, equally a characteristic of the spinous 

 processes of the Coccosteus. In their general proportions, the 

 true Celacanths, if we perhaps except one species, — the Glyp- 

 tolepis Microlepidotus, — were all squat, robust, strongly-built 

 fishes, of the Dirk Hatterick or Balfour-of-Burley type ; and 

 not only in the larger specimens gigantic in their proportions, 

 but remarkable for the strength and weight of their armour, 

 even when of but moderate stature. The specimen of Ho- 

 loptychius Nohilissimus in the British Museum could have 

 measured little more than three feet from snout to tail when 

 most entire ; but it must have been nearly a foot in breadth, 

 and a bullet would have rebounded flattened from its scales. 

 And such was that ancient Celacanth family, of which the 

 oldest of our Scotch ganoids, — the Aster olepis of Stromness, 

 — formed one of the members, and which for untold ages has 

 had no living representative. 



Let us now enter on our proposed inquiry regarding the 

 cerebral development of the earlier vertebrata, and see whe- 

 ther we cannot ascertain after what manner the first true 

 brains were lodged, and what those modifications were which 

 their protecting box, the cranium, received in the subsequent 

 periods. Independently of its own special interest, the in- 

 quiry will be found to have a direct bearing on our general 

 subject 



