STURGEONS. 75 



edge of the upper lobe of the tail fin, which is typically hetero- 

 cercal. The first fin-ray of the pectoral fin is stout and spine-like. 

 The gill-cover is supported by a single plate (opercular bone), and 

 there are no branchiostegal rays. The bones of the cranial roof 

 form a continuous shield, which has a median series of bones, not 

 present in the Chondrosteidse. 



The fifteen or more species of Sturgeon (Acipenser) that are Sturgeon. 

 known occur in the seas, estuaries and rivers of the temperate and 

 northern regions of the northern hemisphere. Most Sturgeons 

 are migratory fishes, living in the sea, but ascending rivers for the 

 purpose of spawning. Although the Sturgeons are not allied 

 to the Salmons and are structurally very dissimilar, there is a 

 strange parallelism in their habits and distribution ; they are both 

 anadromous, living in the sea but ascending rivers to spawn, and 

 are both northern forms, common in Europe and North America, 

 less common in Asia ; in both there are some species or varieties 

 which are non-migratory and confined to fresh water. Sturgeons 

 are ground-feeders and rout about diligently in the gravel, sand 

 and mud for the worms, small fishes, molluscs and crustaceans 

 that constitute their food. The mouth is very protrusible, and is 

 thrust downward as a spout-like tube into the mud. 



The Sturgeons are fishes of considerable economic importance. 

 The flesh, though rich and fat, is esteemed as an article of food, 

 and the ovaries of numerous Russian and American species find 

 their way to market in the form of " caviare." The collection of Caviare, 

 the unshed spawn and its conversion into caviare form an im- 

 portant summer industry near the mouths of the great rivers of 

 Eastern Europe. One of the most important stations is at 

 Rubinsk, on the Volga, where the people collect in thousands in 

 the late spring and await the advent of the fish in the river. As 

 soon as notice is given by a look-out man of the arrival of the 

 shoal, the people attack the fish by nets and spears. The ovaries 

 are taken out, washed in vinegar, and spread upon boards in the 

 open air. Salt is then rubbed in by hand and the caviare is 

 pressed in bags and packed in kegs for the market. In Russia 

 caviare is a regular article of diet, but in the western countries of 

 Europe it is eaten only as a delicacy or a savoury. There is a 

 superior form of caviare which is not salted and pressed, but is 



