THE STURGEONS. 123 



the commencement of a subdivision into lobes; in other 

 wordsj makes a departure from the cartilaginous structure, 

 and the nearest approximation yet discovered to the 

 more complicated form observable in all the osseous 

 orders. 



(109.) The Sturgeons (Sturionid^) form the next 

 aberrant group, of which, at present, only one genus 

 is known. All the species are distinguished by being 

 defended, as it were, by armour, or, at least, having the 

 body covered by hard bony tubercles. The mouth is 

 small ; but instead of teeth it is furnished with a horny 

 prolongation of the jaws, which perform the same office, 

 and are analogous to what we see in the cheloniform 

 fishes. The mouth, however, has this peculiarity, — that, 

 by its possessing a style with three articulations, it has 

 the power of being protruded and retracted at pleasure. 

 The gill- cover is of one oval radiated plate; but the 

 aperture is comparatively small, and its cover, by being 

 edged with a membranaceous border, closes the aperture 

 so accurately as to exclude the air. The food is small 

 fish and worms. 



(110.) The common sturgeon (^A.stiirio Linn. ,^^.8.) 



affords that well known delicacy called Caviar, which is, 

 in fact, the roe of this fish properly prepared and dried. 

 It is usually inclosed in wax, and in this state is sent 

 to all parts of Europe. Sturgeons grow to a very 

 large size, many having been caught that measured 

 more than twenty feet long. Its form is lengthened 

 and slender ; the snout very long in some species ; 

 and the mouth, as in nearly all the cartilaginous 

 fishes, placed beneath. Several cirri, or worm-Hke 

 appendages, are seated beneath the muzzle, and near 

 the mouth ; this latter consists of a transverse oval 



