On the Structure and Position of Eozoon Canadense. 301 



horizontal lamellae, which are connected with each other at 

 intervals by vertical bands • in the npper part, the segments 

 preserve their distinctness to a much greater degree, and are 

 piled one upon another without any regular plan. The exposed 

 surface of the segments, both in the lamellated and in the 

 acervuline portions, is seen to be whitened by the asbestiform 

 layer, also shown as a narrow edging in the sectional view of 

 the lamellated portion. This layer consists of the needle-like 

 siliceous filaments which take the place of the pseudopodia 

 originally, occupying the minute parallel tubuli of the proper 

 walls of the chambers, and which remain in situ after the 

 removal of the calcareous shell that was traversed by them. 

 Between the two lower lamellEe of serpentine, in the broad 

 space originally occupied by a thick layer of the c ' intermediate 

 skeleton," is seen on the right the siliceous model of a small 

 group of stolon-processes, which passed directly from the sar- 

 code body occupying the chambers of the lower tier to that of 

 the tier next above, whilst on the left is shown the internal 

 cast of a part of the canal system, forming a model in ser- 

 pentine of the arborescent clusters of sarcodic prolongations 

 which occupied it. 



Tinted Plate. — Structure op Eozoon. — Fig. 1. Portion of 

 the calcareous shell (restored), the contents of the chambers 

 having been removed. A 1 , A 1 , A 1 , chambers of a lower tier, 

 communicating with each other freely at a, a, and separated 

 from an adjacent chamber at b, b, by an intervening septum 

 traversed by passages. A 3 , A 2 , chambers of an upper tier. 

 B, B, B, B, proper walls of the chambers, traversed, as in the 

 nummuline type, by fine tubules. These tubules are seen, in 

 the upper wall of the chambers, A 2 , A 2 , to pass with uniform 

 parallelism, from the inner to the outer surface, where they 

 open at regular distances from each other ; but in the upper 

 wall of the chambers, A 1 , A 1 , A 1 , the tubules are seen to con- 

 verge in their passage outward, so as to open on the surface .in 

 irregular bands and clusters. C, C, 0, intermediate skeleton, 

 composed of homogenous shell substance, traversed at D by a 

 stoloniferous passage connecting the chambers of two tiers, 

 and at E, E, E by the canal system. 



Fig. 2. Highly magnified portion of the asbestiform layer, 

 left after the decalcification of the shell-wall, showing varieties 

 in the arrangement of the siliceous internal casts of the tubules, 

 which represent the pseudopodia that occupied them in life. 

 At a is shown the uniform surface given by the ends of the 

 closely-packed parallel aciculi, which are seen standing side by 

 side in the sectional view beneath. At 6, the uniformity of 

 surface is interrupted by the partial convergence of the aciculi, 

 leaving vacant spaces between. And at c is shown the more 



