CHONDROSTEI. 99 



brought to Europe, and some are exhibited here. Protopterus, and 

 probably also Lepidosiren, are carnivorous. The Barramunda 

 (Ceratodus, fig. 89) is herbivorous; it is locally plentiful in the 



Fkr. 89. 



The Barramunda {Ceratodus). (From Queensland.) 



Burnett, Dawson, and Mary rivers, and grows to a length of six 

 feet. To the settlers it is known by the name of Burnett or Dawson 

 Salmon. It can breathe either by gills or by its lung alone, or 

 by both simultaneously. Fossil teeth have long been known from 

 Triassic and Jurassic formations in various parts of Europe, India, 

 and America. 



Chondrostei (Cases 29, 30). — The skeleton is cartilaginous, [Cases 

 and the skin is naked or partially protected by bucklers. This ' -I 

 Suborder is divided into two families — Acipenseridce and Polyo- 

 dontidce. To the former belong the Sturgeons (Acipenser), inhabi- 

 tants of the temperate zone of the northern hemisphere ; they are 

 either entirely confined to fresh water, or ascend periodically, for the 

 purpose of spawning, from the sea into rivers. About 20 different 

 species can be distinguished. The best-known are the Sterlet 

 (A. ruthenus) from Russian rivers, celebrated for the excellence of 

 its flesh, but rarely exceeding a length of three feet ; the Hausen 

 {A, huso), from rivers falling into the Black Sea and the Sea of 

 Azow, sometimes 12 feet long, and yielding an inferior kind of 

 isinglass ; the Common Sturgeon of the United States {A. macu- 

 losits), which sometimes crosses the Atlantic to the coasts of Great 

 Britain ; Guldenstadt's Sturgeon (A. gueldenstoedtii) , common in 

 European and Asiatic rivers, which yields more than one fourth 

 of the caviare and isinglass exported from Russia* ; the Common 

 Sturgeon of Western Europe [A. sturio), which is said to attain to 

 a length of 18 feet, and has established itself also on the coasts of 



* In a small table-case between Cases 30 and 31 samples of the best sort 

 of Russian isinglass are exhibited. 



