284 



j 



m « 



h> 



Fin. 291. Acipenscr sturio, 

 the .sturgeon. (From Ship- 

 ley and MacBride's Zoology.) 



SYSTEMATIC ZOOLOGY 



gar pikes. Structurally they form a con- 

 necting link between the Elasmobranchii 

 and the Teleostei, the next order to be 

 taken up. The common sturgeons, which 

 belong to the genus Acipenser (Fig. 291 ), 

 are the largest fresh-water fishes. They 

 occur in North America and Europe, and 

 some of the European species may attain 

 a length of over seven and a half meters 

 and a weight of some 

 1360 kilos. 



They have an elon- 

 gated snout with a tooth- 

 less mouth on the ventral 

 side of the head ; ante- 

 rior to the mouth are 

 four barbels, soft, de- 

 pendent p r c e s s e s . 

 Over each eye is a spira- 

 cle, and five longitudinal 

 rows of bony plates, or 

 scutes, extend backward 

 along the dorsal and 

 lateral portions of the 

 body. There is a dorsal 

 fin, a ventral fin, and a 

 heterocercal caudal fin, 

 and the usual pectorals 

 and pelvics. On the an- 

 terior border of the fins 

 of most of the Ganoidei 

 are scales called fulcra; 

 they are found in no 

 other group of fishes. 

 The skeleton is almost 

 entirely cartilaginous. 

 As in all the Ganoidei, 

 there is a spiral valve in 

 the intestine, and an air 





,1 



Fig. 292. L, 



plafystomus, the t;ar 

 pike. <', caudal fin; 

 d.f, dorsal fin ; fi, ful- 

 cra; /./, lateral line; 



pectoral fin ; 



pelvic fin : v.f. ventral 



fin. (After Cuvier, 



from Parker ami Has- 



- Text-book.) 



