104 
BEPOKT—1847. 
approximation with eacli other. In the tooth also we find a considerable 
variety of structure, in addition to those forms presented by the shell. Thus, 
in fig. 26 is seen a group of large cells, tlm calcareous contents of which are 
disposed in a very regular radiating plan, which looks as if some force had 
been in operation within them, aiialosous to that which produces the siinilsr 
arrangement in radiating Arragonitc or Wuvellite. 'I'hc borders oC this 
g^oup pass into another cluster of cells (fig. 27), that prm‘t»ts no trace of 
this cunous structure (of witich, however, then* are some indications in the 
shell): whilst the latter gradually passes by the obliteration of its ceil- 
boundaries, into a laj'er of very homogeneous iispect. Besides these, tiicrc 
are several curious forms of elongated cells, some- of them with square ter¬ 
minations, as ill fig. 28, and some pointed or fusiform, as in fig. 29. In tliew 
last may be seen transverse .«itrin;, closely resembling those of the long pris- 
matic cells of Piraia, and jirobalily duo to the same cause,^uamely, the 
coalescence of piles ot fiattened cells, whose original ihtehiicss is indicated hv 
the spaces between the strim which indicate their lines of junction. Upuir 
IS ast circumstance I am iljspos<-d to lay much stress, as indicating the 
really compound nature of the long irregtilur fusiform cells, of which ffr 
buve already seen sonic examples, but xvhich an? peculiarly chavociemtic of 
e unna ve grouji. Ncitlmr in the shell nor the tooth of ^uaawuxria'M 
lere aiimial matter enough to give anything more than a delicate membra* 
nous residuum, in winch no vestige of cell-waUs can be traced. 
, 1 u * .i" layer composed of large fusiform cells, 
vliiUt the inner is nearly homogeneous. At tho lines of junction of tlie sue- 
o »«a‘’gjn i.< a yellow layer, probably owing its colour to 
1 r '^1 nmttcr, such as might, if poured out upon tho “up 
hp«n» Ifr ^ Pf’fiostracum. Ii, this layer there is a very definite anti 
l>eing in some parts polygonal and 
(fig. 3^>) whilst In others they are rounded and isolated 
as to nvikn (as is well known) lias not been so strictly defined 
tn all of wh^l, ^ thive s]>cok-s however, 
is move ort , 'verc the same or nearly so. The inner layer 
minute tubes " "*i Bometime.s perforated by very 
the cells are ^ot J nrni'5’'i everywiiorc distinctly cellular, but 
not even come im, ^ ^ 'lefined at their edges (fig. and somctini'Sdo 
with opake m-itf .r^ contact; the space# between them are then filled op 
microscSe tL 7 ?' * Iw^rfeeUy black appearance under the 
S nonTseit Itavc somewlmrof the radiated a^ 
mination’ are fotnd h. bo nmmto projeetioiiB; these on esa- 
posed upim tho nr,mA * ♦ot^'oed by a set of large scattered cells, super- 
described and figured in HieTcL'Tnu^^ resembling those which will be 
oxtcrnaU??CZ^'^^^ definitely exhibit^!. The 
roughened bv a nmn;M?rf r ’ *" ^ ‘'ave examined, « 
fienco of nuiiifmiie t« ® elevations. These are due to the pre¬ 
form a superficial coaHu^ *^^’‘^*^** rdls filled with calcareous matter, which 
the perZtraenm BupHrpo«.d upon the ortlinarv external layer (fig* 
intcnspacLTust aT emitinucd over thorn and sinking down into their 
true skin. The uronpi* nvf*^.** covers the papillafy surface of the 
sharply.boiinH* ■ is composed of polygonal cells, with 
; O hor ‘Z We unclear .spots ^/.^32) strongly re- 
g ^ome of those which present themselves in hm arLria 
