48 ANIMALS OF THE PAST 



bathing in the Miocene ocean unpopular. Con- 

 temporary with the great-toothed shark was another 

 and closely related species that originated with him in 

 Eocene times, and these two may possibly have had 

 something to do with the extinction of Zeuglodon. This 

 species is distinguished by having on either side of the 

 base of the great triangular cutting teeth a little projec- 

 tion or cusp, like the "ear" on a jar, so that this species 

 has been named auriculatus, or eared. The edges of the 

 teeth are also more saw-like than in those of its greater 

 relative, and as the species must have attained a length 

 of fifty or sixty feet it may, with its better armature, 

 have been quite as formidable. And, as perhaps the 

 readers of these pages may know, the supply of teeth 

 never ran short. Back of each tooth, one behind an- 

 other arranged in serried ranks, lay a reserve of six or 

 seven smaller, but growing teeth, and whenever a tooth 

 of the front row was lost, the tooth immediately behind 

 it took its place, and like a well-trained soldier kept the 

 front line unbroken. Thus the teeth of sharks are con- 

 tinually developing at the back, and all the teeth are 

 steadily pushing forward, a very simple mechanical 

 arrangement causing the teeth to lie flat until they reach 

 the front of the jaw and come into use. 



Once fairly started in life, these huge sharks spread 

 themselves throughout the warm seas of the world, for 

 there was none might stand before them and say nay. 

 They swarmed along our southern coast, from Maryland 

 to Texas; they swarmed everywhere that the water 

 was sufficiently warm, for their teeth occur in Tertiary 

 strata in many parts of the world, and the deep-sea 

 dredges of the Challenger and Albatross have brought 

 up their teeth by scores. And then they perished, 

 perished as utterly as did the hosts of Sennacherib. 

 Why? We do not know. Did they devour everything 



