17 



ton is either naked, plated or scaled. The arterial bulb is 

 muscular and contractile with many valves ; the air bladder 

 has a pneumatic duct ; the intestine a spiral valve. The ter- 

 minal point of the notochord is never ossified. The embryo is 

 sometimes provided with external gills. 



Family Accipenseridae. 



Sturgeons. 

 This family of Ganoids, which were so numerous in earlier 

 geological times, is characterized by the long fusiform body; 

 the skin is covered with five rows of bony keeled shields, be- 

 tween which are smaller plates. The snout is long, the mouth 

 inferior, protractile and toothless ; there are four barbels in a 

 row in front of the mouth. The maxillary is present, the 

 opercle rudimentary. The vertical fins have springlike projec- 

 tions on the front rays, called fulcra. There are four gills, no 

 branchiostegals. The ova are fertilized after extrusion, as in 



most fishes. 



Accipenser sturio L. 



Sturgeon. 

 The common sturgeon is found along the Atlantic coast 

 from the Carolinas northward ; it is anadromous and common 

 in the Hudson River, where it is regularly fished for. This is 

 one of the fishes now being re-introduced by the U. S. Fish 

 Commission in many rivers from which it has well nigh disap- 

 peared. The Sturgeon grows to an extreme length of twelve 

 feet. It is a food fish of no low rank. 



Accipenser brevirostrum Les. 

 Short-nosed Sturgeon. 

 This species has a blunt snout which is much shorter than 

 the rest of the head. It occurs from Cape Cod to Florida, but 

 is much scarcer than the previous species. 



Series Teleostei. 



Bony or True Fishes. 

 Under the head of Teleosts comes the vast majority of 

 modern fishes. The skeleton is ossified, the vertebrae are com- 

 pletely formed, the tail is not distinctly heterocercal in adults, 

 it is in a few cases diphycercal but generally homocercal. The 



