B. SKELETON. 



I. DERMAL SKELETON 



THE dermal skeleton, ;is jiliylogenotically the older, is best 

 considered before the endoskeleton. Its relative age is shown 



a 



FIG. 17 (.-il'tiT ". H'Ttuii,'). ". ]>II:\IM, AI:\IAIM;I OF //< /<"*/",//" communt 



Silurni.l) : l>. DENTICLES M:M\I 1111. SKIN oi'TJM-: A i:]>"\i I s "! ' W//.7///// ; c, 



PtATBe 1 l:"\| I II I 'I'M I, -KIN 111 



/.. .li-iiii. il .l.'iili'-li's, sin. \\ it liioki-n nil' I'rnm (ln-ir luisrs ;it 7S ; 1:1'. l.;i-;il ]il:itr. 



in.! milv l>v PalflBOntology, 1 but :dsn b\ ( hitii^cny. inasnuicli us 

 (.ilcitir.-iiii.ns :md (tssilifiitions in tlic derma <>r perichondrmm 



1 A.a examples of oncieul fuiin- \\hirli VM-V^ ].ruirrtni i.\- well-developed ilcrnml 



skclrtuli-. ln;iy !" ini-lit ii .ln-il lln- :il innUI n| I''i--lii-.s of lln- I )r\ i.n l:i n ami Silurian 

 .liatii, :ui' I tin- in ii 1 1 ill n -il Amj'liil'i.m "^ the ' ,1 1 i - MII I. n ,us. Trins, ami . 



