﻿Animal Nature of Eozobn Canadense. 71 



it equals anything I have seen in calcareous organisms of 

 later periods. This state of perfection is, however, 

 naturally of infrequent occurrence. The finer tubuli are 

 rarely perfect or fully infiltrated. Even the coarser 

 canals are not infrequently imperfect, while the lamin?e 

 themselves are sometimes crumpled, crushed, faulted, or 

 penetrated with veins of chrysotile or of calcite. In some 

 instances the calcareous laminae are replaced by dolomite, 

 in which case the canal-systems are always imperfect 

 or obsolete. The laminae of the test itself are also in 

 some cases replaced by serpentine in a flocculent form. 

 At the opposite* extreme are specimens or portions of 

 specimens in which the chambers are obliterated by 

 pressure, or occupied only with calcite. In such cases the 

 general structure is entirely lost to view, and scarcely 

 appears in weathering. It can be detected only by 

 microscopic examination of slices, in parts where the 

 granular structure or the tubulation of the calcite layers 

 has been preserved. All palteontologists who have 

 studied silicified fossils in the older rocks are familiar 

 with such appearances. 



It has been alleged by Mobius and others that the 

 canal-systems and tubes present no organic regularity. 

 This difficulty, however, arises solely from imperfect 

 specimens or inattention to the necessary results of slicing 

 any system of ramifying canals. In Eozoon the canals 

 form ramifying groups in the middle planes of the laminae, 

 and proceed at first almost horizontally, dividing into 

 smaller branches, which ultimately give off brushes of 

 minute tubuli running nearly at right angles to the 

 surfaces of the lamina, and forming the extremely fine 

 tubulation which Dr. Carpenter regarded as the proper 

 wall. In my earlier description I did not distinguish this 

 from the canal-system, with which its tubuli are inwardly 

 continuous ; Dr. Carpenter, however, understood this 



