TURTLES AND TORTOISES 43 



to be courtship, but the resounding thumps are like the 

 blows of a heavy mallet or a sledge and look far more 

 ludicrous than romantic. At such times the males utter 

 deep, trumpeting calls. 



It is quite probable that the colony of these strange 

 creatures in the New York Zoological Park will survive 

 to be exhibited to several future generations and that 

 their stony gaze upon man's affairs may coldly observe 

 conditions comprehended by us, of the present, only in 

 our most speculative dreams. In time to come the morn- 

 ing sun-bath of these tortoises may be momentarily 

 darkened, now and then, by the flight of passing air 

 ships bringing visitors to the great institution, there to 

 look, to wonder, and then to realize that the creatures 

 before them— living remnants of the army of giant fos- 

 sils — speak mutely of an epoch when their ancestors were 

 the masters of the globe, fully as dominant as man has 

 finally become. Could there be a more stirring illustra- 

 tion of the ages through which our planet has passed? 



Leaving the Testudinidce and its varied forms that are 

 adapted to such strikingly different modes of life, we 

 arrive at another branch of the Cryptodira, a highly 

 specialized family of turtles that have taken to the sea 

 and developed seal-like flippers. In the possession of 

 these they resemble the Leathery Turtle, Spargis, but 

 the parallelism relates only to a certain development of 

 the organs of locomotion that is imperative in a marine 

 life. 



Family Chelonidce; Sea Turtles : Two genera, each 

 containing two species, make up the family. Three 

 of the species have an extensive distribution, being 

 found in all tropical and semi-tropical seas of the globe. 

 They are the giants of the aquatic chelonians and ex- 



