528 



THE POPULAR SCIENCE MONTHLY. 



Every one sees at a glance that the sharks (Figs. 5, 6, 1) are 

 widely different from all ordinary fishes. Their peculiar outline in 

 general, their unequal-lobed tail, their transverse mouth on the un- 

 derside of the head, their formidable array of lancet-shaped teeth, 



Fig. 6. Thresher-Shark (Alopias vulpes, Bonaparte). 



tlieir fixed gills without gill-covers, their rough skin, their pillow- 

 shaped eggs with long, tendril-like appendages at the corners (Fig. 

 8), all combine to separate them about as far as possible from typical 

 fishes. And if we compare them with one another, what wonderfuUy- 



FiG. 7. Hammer-head Shark {Zygcena malleus. Valenciennes) ; and Sawfish (Pristis anti- 

 quorum, Latham). 



diversified forms do we see as we pass from the dog-sharks to the 

 mackerel-sharks, and from the latter to the white sharks, and from 

 these to the threshers, and to the hammer-heads, and so on through 

 the whole list ! 



And who that has studied only the ordinary fishes would at length 



