50 SUPPLEMENT ON 



being misunderstood, where so many different names have 

 been given to the same objects, the nomenclature and ter- 

 minology of the author have been retained in the version even 

 at the risk of using gallicisms. 



ON THE TEXTURE OF THE BONES OF FISH l . 



The skeletons of fish are either bony, fibro-cartilaginous, or 

 really cartilaginous ; the last-mentioned, constitute the chon- 

 dropterygian fish, who have in the whole of their framework ; 

 in their branchiae, the external border of which is fastened to 

 the skin, allowing water to escape by means of narrow and 

 multiplied openings ; as well as in other marked details of 

 organization, distinctions which obviously separate them 

 from all other fishes. They are without real bones, the hard 

 parts being internally only cartilage, homogeneous, and semi- 

 transparent ; merely covered on the surface in rays and 

 sharks, by small opake and calcareous granules, closely placed 

 together ; but lampreys are without this superficial addition, 

 and in ammocetes, the remaining one, the skeleton is in a 

 really membranous state. Sturgeon and chimserae have their 

 spines soft like lampreys, but the first-mentioned genus is 

 possessed of many bones of the head and shoulder, of which 

 the blade on the surface is completely hardened and ossified. 



Other fishes differ in this respect, simply in the relative 

 hardness of the parts of their skeletons, and the fibro-cartila- 

 ginous genera have been associated without cause with the 

 chondropterygians. Mixed with the cartilage which con- 

 stitutes the basis of their bones, the calcareous matter or 

 phosphate of lime is disposed in fibres and layers, in the 



1 Cuv. Hist, des Pois. chap. iii. 



