161 
THE GEOLOGICAL MIDDLE AGE. 
long and conical, placed at considerable intervals 
in the jaw, constitute a feature common to all 
predaceous aquatic animals, and would seem to 
l ia ^ o been utterly useless in a flying animal at 
that time, since there were no aerial beings of 
any size to prey upon. The Dragon-Flies found 
in the same deposits with the Pterodactylus were 
certainly not a game requiring so powerful a bat- 
tery of attack. 
the Fishes of the Jurassic sea were exceedingly 
numerous, but were all of the Ganoid and Se- 
lachian tribes. It would weary the reader, were 
I to introduce here any detailed description of 
them, but they were as numerous and varied as 
those living in our present waters. There was 
the Hybodus, with the marked furrows on the 
opines anc ^ the strong hooks along their margin, 
— the huge Chimera, with its long whip, its 
curved bone over the back, and its parrot-like 
bill, the Lepidotus, with its large square scales, 
its large head, its numerous rows of teeth, one 
within another, forming a powerful grinding ap- 
paratus,— the Microdon, with its round, flat 
body, its jaw paved with small grinding teeth, 
the swift Aspidorhynchus, with its long, slender 
body and massive tail, enabling it to strike the 
water powerfully and dart forward with great ra- 
pidity. . There were also a host of small Fishes, 
comparing with those above mentioned as our 
