THE STERLET. 47 



grey, but the plates are dirty white, like the under-side of the body. The barbels are flattened, and 

 nearer to the eye than to the end of the snout. It is only occasionally found in the Mediterranean, 

 and is otherwise confined to the Black Sea and Sea of Azov, and the rivers which flow into them. 



The Acipenser rutkenus, commonly known as the Sterlet, is a small species, rarely more than 

 twenty-one inches long. It has a narrow, pointed snout, which is somewhat elongated. The barbels 

 are slightly fringed. The number of dorsal shields vaiies from eleven to fourteen. The lateral shields 

 are more numerous than in any other species, and ai*e from sixty to seventy in number. The skin 

 is densely covered with minute ossifications, which are uniform in size. The back is a very dark 

 grey, but the shields are whitish like the belly. It is found in the Black Sea, and in all the rivers 

 which flow into it. It is a regular article of food at Vienna, is sometimes taken at Linz, and 

 occasionally ascends as far as TJlm. It is abundant in the Caspian and the rivers that empty them- 

 selves into it ; but less plentiful in the rivers of Siberia. It is believed to extend into the north- 

 west coasts of America. Acipenser rutkenus deposits its eggs when the water has a temperature of 

 54 Fahr. The eggs are sometimes fecundated artificially in the Volga. The young are developed in 

 seven days. They are at first a quarter of an inch long, but in ten weeks increase to a length of two 

 inches, feeding chiefly on the larvae of insects. They can live in fresh water only, but are hardy, and 

 are often transported overland. In this way it was introduced long ago into Pomerania and Sweden. 

 Several different species, distinguished by the form of the snout, the number of osseous shields, and 

 the rays in the dorsal fin, occur in California, the Mississippi, and great lakes of North America. 

 Other species are confined to the Atlantic coast of the United States. Sturgeons, however, are 

 not found in North America north of latitude 54, where the mean annual temperature is 33 Fahr. 

 They are not often seen in clear cold streams, but make their way up many muddy rivers in such 

 numbers as to form almost the only food of the Indian tribes during the summer months. The 

 Acipenser brevirostris, which is usually from two to five feet long, is so abundant in the river Hudson 

 as to be known in the markets under the name of Albany beef. One species (A. sinensis) is known 

 only from China, and is reserved for the table of the Emperor. Two or three species appear to be 

 limited to the Mediterranean, but the majority of Sturgeons are confined to the Black and Caspian 

 Seas, and the rivers which flow into them. 



FAMILY IT. POLYODONTID^E. 



A second family in this order is formed for the Paddle-fish genus, named Polyodon. It is 

 represented by two species, one (Polyodon folium} found in the Mississippi and its tributaries, 

 the other (Polyodon gladius) occurring in the Yang-tse-kiang. The genus differs from the Sturgeons 

 in having the skin naked, or containing only minute star-shaped ossifications. The snout is 

 extremely long and shovel-like. It is covered with small star-like reticulations, and is regarded 

 by Wagner as being a forward prolongation of the pai'ietal region of the skull. The maxillary 

 arch is fixed to the head, so that the mouth cannot be protracted as among the Sturgeons. The 

 jaws are armed with minute teeth, and there are teeth on the palatine bones. There are no 

 barbels, and there is no tongue, so that the sense of touch must be feeble. The fins resemble 

 those of the genus Acipenser, except that the lower lobe of the caudal fin is nearly as broad as 

 the upper lobe. The air-bladder is large and cellular, and opens into the oesophagus. There is 

 hardly any separation between the oesophagus and the stomach ; the pancreas is a short broad 

 lobed organ ; and the intestine terminates in a spiral valve. The cartilaginous rings of the vertebral 

 column are more delicate than those of the Sturgeon. 



