EOZOON 



839 



of 'storeys' of chambers (fig. 641, A 1 . A 1 , A-, A 2 ), the chambers 

 of each ' storey ' usually opening one into another, as at a, a, like 

 apartments en suite, but being occasionally divided by complete septa . 

 as at 5, b. These septa are traversed by passages of communication 

 between the chambers which they separate, resembling those which, 

 in existing types, are occupied by stolons connecting together the 

 segments of the sarcode-body. Each layer of shell consists of two 

 finely tubulated or ' Nummuline ' lamellae. B, B, which form the 

 boundaries of the chambers beneath and above, serving (so to spe;ik) 

 as the ceiling of the former, and as the floor of the latter ; and of 

 an intervening deposit of homogeneous shell-substance C, C, which 

 constitutes the ' inter- 

 mediate skeleton.' The 

 tubuli of this ' Xum- 

 muline' layer (fig. 643) 

 are usually filled up (as 

 in the Nummulites 

 of the ' Nummulitic 

 limestone ') by mineral 

 infiltration, so as in. 

 transparent sections to 

 present a fibrous ap- 

 pearance ; but it for- 

 tunately happens that 

 through their having 

 in some cases escaped 

 infiltration the tubu- 

 lation is as distinct 

 as it is even in recent 

 Nummuline shells (fig. 

 643). bearing a singu- 

 lar resemblance in its 

 occasional waviiiess to 

 that of the crab's claw. 

 The thickness of this 

 interposed layer varies 



FIG. 641. Portion of the calcareous shell of 



canadense as it would appear if the serpentine 

 that fills its chambers were dissolved away : A 1 , A 1 , 

 chambers of lower storey opening into each other 

 at , a, but occasionally separated by a septum, 

 b, b ; A 2 , A-', chambers of upper storey ; B, B, 

 proper walls of the chambers, formed of a finely 

 tubular or Nummuline substance ; C, C, inter- 

 mediate skeleton, occasionally traversed by large 

 stolon-passages, D, connecting' the chambers of 

 different storeys, and penetrated by the arbores- 

 cent systems of canals, E, E, E. 



considerably in differ- 

 ent parts of the same mass, being in general greatest near its 

 base and progressively diminishing towards its upper surface. 

 The 'intermediate skeleton' is occasionally traversed by large 

 passages (D), which seem to establish a connection between the 

 successive layers of chambers ; and it is penetrated by arborescent 

 systems of canals (E, E). which are often distributed both so 

 extensively and so minutely through its substance as to leave 

 very little of it without a branch. These canals take their origin, 

 not directly from the chambers, but from irregular lacinni 1 or 

 interspaces between the outside of the proper chamber-walls and 

 the 'intermediate skeleton,' exactly as in <~'(ilcnriiifi. the exten- 

 sions of the sarcode-bodv which occupied them having apparently 

 been formed by the coalescence of the pseudopodial filaments that 

 passed through the tubulated lamella 3 . 



