122 
REPORT-1847. 
another circle of solid pillars, whose transverse sections are seen at (fig, 
65). The same arrangement may be repeated many times. On looking >1 
the outer border of the section, we observe tliat the rounded sides of lie* 
pillare form a series of projections (figs. 65 and 67, c, c) with hollows !*■ 
tween them; and these exactly correspond with tin* projectingrilwand 
rows which we may notice running along the natural surface of tlie ^ 
when we examine tliis with a magnifyiug-glass, or even (in some iusunco) 
with the naked eye. There is considerable difiV-rence in the spinw of 
various species with rt'gard to the <legree of proximity, and to the natUKjf 
tlie connection, of these solid pillars. In soiuo instancrt they secra to bedfr 
tached from each other, each being united to iJie adjoining ones and to ik 
interior substance merely by the general fibro^alcareous network ^as in fig, 
65). But in other eases we observe that they obviously send prolongstioM 
inwards, whoso arrangcnient corresponds witli that of llic medullary rand 
the exogenous stem ; these prolongations arc sometimes lost amid the hbnr 
ca.lcarcou3 network (figs. 68, 69); but in other instances tlmf pa» 
without altogether losing their solid character, and abut against the eitwicr 
of the row of pillaiw which bounds the layer within (fig*. 70,72> Even a 
this latter case, whilst we can eh-arly trace inwards the solid plates until liny 
become continuous with the [lillars of the next interior layer, we obscrvelbs 
they are tmvcised by thifada of the same tibro-calcareous netwark; aadii 
seems rather difficult to j-cconcile the idea of thu solidity of the platfs 
the fact, that wherever wc cut across tliis structure wo observe the netvod 
^ Ihe whole space from oiio circle of pillars to the uext. »•' 
shall find the explanation of this, however, in the struotun* which the biigi* 
tudinal section reveals to us. When wo examine a thin slice taken :atli( 
latter direction in such a manner that thu plane of the section panscs tbi'ingii 
any dtatmier of the transverse section (so as to pass along with the radiaw? 
plates and not across them), we sec thu contro of the spine ocoupk'il, Mb' 
lore, with the nbro-tmluarooiis network, ft*riiiing a medulla, in whiih noie- 
gulur pattern IS discurniblo (fig. 73, a). Tliis is bordumd on cither M 
rif U? and upon a careful examination of thu, U* 
tound that »ts inner border passes insensiblv, as it were, into the 
wreo^ network, the solid part of which springs from it. oa lotfc 
either snie, we observe that the network ro-appears (as 
sverse section), but tiuit it gradually assumes a more regular chaiacW 
ratheri'ls exterior, fo as to proEnl 
tovrf,* . 1 “"‘' 0 “““. i>l"le « ithpcl*ratioDs»treg»to!^ 
.mailer luid s»ailler, «o ttat 
cZL nTrl ‘l-e .ub.,a„c*,-ua.il we 
eatonor of Uic layer, where we Ime them altoeethcr, aud iuslead of tbf 
had ti e aiwlar .truottiro rocoaimeufing, and aa^n oaBiag sradMlIr »» 
aver TW mA”'.'- 
Si, iTl fr"” “•ui.lar structure into the impetfouUe pl»^» 
at am- oob , ‘'‘uu tl-ut a traaevei* «uon 
pSirwhi*, “ ' ".''1*'“* '>‘^P‘U^rs,bb, comiilctely»oliJ>>:*^ 
redcS ebr. "'"y " ‘'I always oahibit »a.e.W 
verso seett a r":-a-^ J'“‘ alluded to, as eiUibitcd by lie 
«nr«« different spines, are presented abo bv die vortical; 
xntonnT structure of the ribs in ererw 
(fig layer the one here 
g ), whilst m otlicrs tlie vertical plates of every layer pass with 1 ““^ 
