88 



PRIMITIVE LIVING SHARKS 



Rece?tt SJiarks 



The forms of Sharks and Rays 

 common at the present time are 

 generally looked upon as closely 85 

 related genetically, although 

 their lineage cannot be defi- 

 nitely traced. As far as palae- 

 ontological evidence goes, they 

 may well have been derived 

 from a single Palaeozoic an- 

 cestor. 



Perhaps of all recent forms, 

 CJilamydoselacJic (Fig. 92), and 

 Notidaiius (Heptanchus, or Hep- 

 tabranchias) (Fig. 93), which are 

 universally regarded as *' primi- 

 tive," have inherited most di- 

 rectly the features of this gen- 

 eralized Palaeozoic form. But 

 which of these two sharks must 

 be regarded as resembling its re- 

 mote ancestor the more closely 

 seems to the writer a very doubt- 

 ful matter. Chlamydoselache 

 derives its great interest from 

 its late discovery (1884, Gar- 

 man), rareness, and Pleuracan- 

 thid type of teeth (Fig. 92, A) ; 

 but now that it has been taken 

 in numbers — comparatively — 

 in deep water, one is inclined 

 to believe that many of its 



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