THE PRESERVATION OF EOZOON. 123 



ting with picrosmine, and surrounding masses of Eozoon in 

 the Laurentian limestones of that region ;* the Eozoon itself 

 being there injected with a hydrous silicate which may be 

 described as intermediate between glauconite and chlorite in 

 composition. The mineral first mentioned is compared by 

 Hoffman to fahlunite, to which jollyte is also related in physical 

 characters as well as in composition. Under the names of 

 fahlunite, gigantolite, pinite, etc., are included a great class of 

 hydrous silicates, which from their .imperfectly crystalline 

 condition, have generally been regarded, like serpentine, as 

 results of the alteration of other silicates. It is, however, 

 difficult to admit that the silicate found in the condition 

 described by Hoffman, and still more the present mineral, 

 which injects the pores of palaeozoic Crinoids, can be any other 

 than an original deposition, allied in the mode of its formation, 

 to the serpentine, pyroxene, and other minerals which have 

 injected the Laurentian Eozoon, and the serpentine and 

 glauconite, which in a similar manner fill Tertiary and recent 

 shells." 



(C.) VARIOUS MINERALS FILLING CAVITIES OP FOSSILS IN THE 

 LAURENTIAN. 



The following on this subject is from a memoir by Dr. Hunt 

 in the Twenty-first Report of the Regents of the University of 

 New 7ork, 1874 : 



" Kecent investigations have shown that in some cases the 

 dissemination of certain of these minerals through the crys- 

 talline limestones is connected with organic forms. The ob- 

 servations of Dr. Dawson and myself on the Eozoon Canadense 

 showed that certain silicates, namely serpentine, pyroxene, and 

 loganite, had been deposited in the cells and chambers left 

 vacant by the disappearance of the animal matter from the 

 calcareous skeleton of the foraminiferous organism; so that 

 when this calcareous portion is removed by an acid there 

 remains a coherent mass, which is a cast of the soft parts of 



* Journ. fur Prakt. Chemie, Bd. 106 (Erster Jahrgang, 1869), p. 

 356. 



