THE STURGEON 17 



whilst there are five longitudinal rows of large 

 bony scutes on the body, a mid-dorsal and paired 

 lateral and ventral series ; the primitive scaling is 

 retained on the upturned part of the tail ; another 

 peculiarity is the presence on each side of a strong 

 pectoral spine, formed by the fusion of the anterior 

 fin-rays. 



The Sturgeons are mostly anadromous fishes, 

 living in the sea and entering rivers to spawn, but in 

 some of the large lakes and rivers of North America 

 they have become permanent residents. They are 

 very variable, change greatly during growth, and also 

 hybridize to a considerable extent, so that there has 

 been considerable difference of opinion as to the 

 number of species entitled to recognition; it is 

 generally agreed that there is only one species in 

 Western Europe, but some authors are of opinion 

 that a second species may occasionally cross the 

 Atlantic from America and enter European rivers, 

 a matter which is dealt with below. 



The Sturgeon (Acipenser sturio) has the body 

 elongate, subcylindrical anteriorly and tapering 

 posteriorly. The size, shape, and arrangement of 

 the bones which cover the upper surface of the head 

 are subject to great variation ; thus the frontals may 

 be in contact for the whole of their length, or may 

 be completely separated by an ethmoidal plate. 

 The snout is covered above with small bony plates 

 and is rather long ; in young specimens it measures 

 at least half, and in examples of from 2 to 3 feet 

 not much less than half of the length of the head, 

 but in large fish only about one-third ; the insertion 

 of the barbels is nearly equidistant from the mouth 

 and the tip of the snout in young and half-grown 



