ANALOGIES OF THE CARTILAGINES. 153 



may yet become of the greatest importance in our en- 

 deavours to determine the different relations which 

 subsist between animals^ whether by affinity or analogy. 

 (134.) Our next comparison is between the stur- 

 geons and the cheloniform fishes, or, in other words, the 

 SturionidcB and the Plectognathes of Cuvier. This 

 analogy will not detain us ; for the very aspect of the 

 two is quite sufl5cient to show us we are following in 

 the right track. The types of both are incased, as it 

 were, in armour ; the head and body being defended by 

 large bony plates, which either compactly join at their 

 sutures, as in Tetraodon, or assume the form and sub- 

 stance of little targets or shields having a sharp central 

 spine ; the mouth, in both groups, is very small ; and 

 the absence of true teeth in both is supplied by an acute 

 elongation of the jaws. This latter character, which is 

 one of the primary distinctions of the cheloniform fishes, 

 is found still more developed in the next type of the 

 cartilaginous order ; and this at once brings us to the 

 only remaining analogy, namely, that between Chimcera 

 and the apodal or anguilliform fishes. Now, it may be 

 observed, that throughout the whole of the cartilaginous 

 groups which we have yet noticed, there is not one 

 which gives us any idea of that slender and attenuated 

 form which belongs to the eels among fish, and to the 

 serpents among reptiles ; and yet in the Chimoera we 

 actually see a fish having the fore part of a shark, and 

 the tail, or hinder part, of an eel. Thus does Nature 

 combine her primary forms : and yet, that analogy should 

 preserve a due subordination to affinity, the primary 

 characters, as well as the whole aspect, of these singular 

 shaped fishes, are decidedly those of the true Cartila- 

 gines, yet so modified as to point out its relations to 

 other groups. Of all the cartilaginous fishes yet dis- 

 covered, the CMmcsrce are those only that have the 

 second dorsal fin very narrow, excessively long, and 

 gradually tapering to the point of the tail ; being all but 

 united to the caudal fin. This latter character, as is 

 well known, pervades the whole of the anguiUiform 



