f 



154 



The Ottawa Naturalist. [October 



hibit. This is the more to be regretted as the specimen was about 

 five feet in length, and much larger than any known to have been 

 before taken in the Dominion. Old fishermen near Point Edward 

 on the Lambton county shore vaguely refer to other specimens of 

 Polyodon occurring in Lake Huron ; but on the other side of the 

 watershed which bounds the southern margin of our western great 

 lake system, that is, in tht basin of the Mississippi River, and in 

 the lakes of the central plateau of the United States, the Paddle- 

 nosed Sturgeon is said to be common. Curiously enough it in- 

 habits the Yang-tse-Kiang and certain Chinese waters ; but else- 

 where this remarkable fish is unknown. What is the meaning of 

 this sparse distribution in such widely separated localities? Again, 

 why is it so rare in our own lakes, and common in the great river 

 basin to the south ? The naturalist's answer is obvious. It is a 

 fish that was once probably widespread in both the old and new 

 worlds. It is indeed a Ganoid, a group of fishes which preceded 

 our existing kinds, and formerly predominated on our planet. 

 Their fossilized remains are familiar to the geologist in the Palaeo- 

 zoic strata. In the ancient world, especially in the Devonian 

 Age, the Ganoid fishes abounded. At the present time the exist- 

 ing species are few, not more than twenty or thirty in all, as com- 

 pared with 12,000 species of living Teleosteans. Their distribu- 

 tion is erratic and very local. Excepting the common Sturgeons 

 (the family Acipenseridae) the surviving species of Ganoids are 

 amongst the rarest of fishes, and Polyodon amongst them, is the 

 rarest of all, and in Canada apparently almost extinct. One would 

 expect to find in the case of any tribe of animals which are dying 

 out, that they would survive here and there in isolated areas, and 

 in some such localities would become more and more scarce. 

 Thesefeatures in the occurrenceof an animal arethesurestsigns of its 

 approaching extinction, and such signs appear in the most marked 

 manner in the case of Polyodon. The exceeding rarity of speci- 

 mens in our waters has called forth the suggestion that those, 

 which are at long intervals captured in our great lakes, are not sur- 

 vivors or descendants of Spatularoids indigenous to Canada ; but 

 wanderers that still find means of migrating across the watershed 

 ot the Mississippi. It is more probable, however, that a few pairs still 



