——— ee nae 
ge 
a 
. 
CTENACANTHUS, A SPINE OF HYBODUS. 155 
number on each side of it. I have also seen oe teeth with 
the ne ag denticles egual in number, but asing in size 
i We ha 
ut 
called Cladodas rea wy Ley ze - hc but are situa 
yale another of those ‘eta that further research has 
proved to have ene during a protracted period, and that tends 
to break down the artificial barrier between Palzozoie and 
Mesozoic times. 
* See my paper with engravings proving this in the begieme’ and March 
numbers of the “Monthly Review of Dental Surgery” 
