:_;() 



.KtHAN KlyER. 



SEC. ARCT. EXP. I'KAM 



(if the slruehire, althonoh of course transformation liv pvrites liail il> 

 unpleasant effects. 



PI. in. fiL;s 5 — 6 are du'ccl |ilioloi;rapli^ of niv microscopic sections 

 and in coniparison \villi llie olln-r illiisliations of microsco|iic .sections of 

 PsaiiiiiiosteiiS remains, show a com|ilete a,t,'reenieiil with thai j<enus. 

 I'ii;. 1), liii llie text) i;i\es n^ a more liiagramatical view of Ihi.^ strnclnre 

 Willi clearer ilelail.s. Il passes troiii^li hotli the n|i|)er ami the lowei- 

 lioiK plate. The fish has hci-ii pressed so slroiit,d\' m ilie schist-, that 



Fig. <i. Sl<rlrh ^liiiwiLig llie v|i-uiliii-r III' llir iliTiiial skclehm in Diepaiiaspis 

 GeiiiiiiKleiieiisiv. isciiLuTEi!. Tlir scrhiiii 1^ iii.ide llirougli one of tlie upper anl one 

 lit' 1lii' lower lioily plates. Tlie l.iller are so greatly eompressed tliut the inmost 

 layer nl' llie ^krlrloii is eriislied. Al the extreme li.p and liiittoni we see tlie den- 

 tiele-. «illi llieij' wide pnip ea\ilies and line dentine tuhnles; Ijelow thenj is ttie 



\a^eiilar eaiial sy^leni. 



hiith III these plates have pressed aL;ainst each other and parllv crushed 

 ill the inner parts. ()llier\vise in this and in the said plale we see the 

 vascular canal system, willi narrow canals and ori[ic(\s in llie upper part 

 and more open ones in the lower. Thus on the up|)er surface we have 

 llie denticles with fine dentine tiihules and \'ery wide pulp cavities. 

 \vhicli are in connection hy means of a hroad orifice with the underlying 

 vascular canals. By their characteristic form, these denticles constitute 

 the surface sculpture. This was not very thoroughly described in 

 Traoijair's works, nor do ids illuslrations convoy so exact a picture 



