432 ZOOLOGY. 



while the air-bladder is cellular, lung-like. Fossil species oc- 

 cur with those of Amid in the tertiary rocks of the West. 

 Lepidusteus osseus Agassiz, the bony gar, with a long, slender 

 snout, is sometimes rive feet long ; L. platystomus Rafin. 

 has a short nose, while the alligator gar, L. spatula Lace- 

 pede, has a short and wide snout, and grows to a larger size 

 (nearly three metres) than the other species, and inhabits 

 the Mississippi Valley. The garpikes are carnivorous, very 

 rapacious, and are said to destroy large numbers of food- 

 fishes. They usually remain near the surface of the water, 

 emitting bubbles of air and apparently taking in a fresh 

 supply. Wilder has observed Amid inhaling air, and re- 

 marks that "so far as the experiments go, it seems probable 

 that, with both Amid and Lepidosteus, there occurs an inha- 

 lation as well as exhalation of air at pretty regular intervals, 

 the whole process resembling that of the Menobranclius and 

 other salamanders, and the tadpoles, which, as the gills 



Fig. 398. Garpike. From Tenney's Zoology. 



shrink and the lungs increase, come more frequently to the 

 surface for air." Both of these fishes are very tenacious of 

 life and withstand removal from water much better than 

 bony fishes and sturgeons, on account of the lung-like nature 

 of their air-bladder. Wilder shows that there is a series of 

 forms, mostly Ganoids, from the Amid and Lepidosteus in 

 which the pneumatic duct enters the throat on the dorsal 

 side, up to Lepidoxiren in which it enters the throat on the 

 ventral side, like the air-tube or trachea of Amphibians and 

 higher Vertebrates. 



The breeding habits and external changes in form of the 

 garpikes have been described by Mr. A. Agassiz. The gars, 

 which are nocturnal in their habits, appear on the shores of 

 Lake Ontario,near Ogdensburg,in immense numbers between 



