292 CARTILAGINEI. 



of maxillaries and intermaxillaries, are reduced, 

 throughout the Order, to mere rudiments con- 

 cealed beneath the skin : and the functions proper 

 to them are performed by other bones of the 

 mouth, as the palatals^ and the vomer. 



Most persons who have ever looked at the 

 backbone of any ordinary fish that is brought to 

 table, — a Mackerel, a Cod, or a Salmon,— are 

 aware that each vertebra is hollowed into a 

 funnel-shaped cavity on each face, which is filled 

 with a gelatinous substance : and that the centre 

 is pierced with a slender hole, through which this 

 jelly passes, thus forming a continuous cord, 

 dilated and contracted alternately, throughout 

 the spine. In many species of this Order the 

 gelatinous cord varies very little in its diameter ; 

 and in some, the central tube of communication 

 is so much enlarged as to reduce the solid part to 

 a mere ring of cartilage. 



It is observable that this Order presents us 

 with some fishes having peculiarities of organi- 

 zation of a higher type than is found elsewhere 

 in the whole Class, exhibiting a close affinity 

 with the Reptiles ; and even making a distinct 

 approach to the Cetaceous Mammalia. "The 

 viviparous Sharks," says the learned author of 

 Horas Entomologicae, " such as the Basking- 

 Shark {Selache maxima, Cuv.), with their ear 

 more perfectly organized than that of other fishes, 

 and their body destitute of scales, the particular 

 disposition of their fins, and their closed branchice, 

 all indicate at what place we are to enter among 

 the fishes upon leaving the Cetaceous quadru- 

 peds."* 



* Hor. Entom. 272. 



I 



