1871.] 197 [Burbank. 



dance of the " tubuli " in bundles, and radiating and branching forms. 



The undulating line that divides this specimen illustrates the 

 banded structure that often appears in the rock. The tubuli are 

 found on both sides of this line, but are most abundant in the part 

 which shows the coarser structure. 



Fig. 2 (also from Chelmsford) shows at the base a mass of the ser- 

 pentine intersected by narrow seams of chrysotile, and attached to a 

 portion of the rock in which the decalcified spaces show the tubuli in 

 great abundance, attached to the serpentine grains as if growing out 

 from their surfaces. Some of the grains are surrounded by a fibrous 

 layer, closely resembling the "true cell wall" of Eozoon, as I have 

 seen it in the Canadian specimens. The surfaces of many of the 

 grains are covered with acicular crystals penetrating the calcite. 

 Some of these, as they extend into the calcite, become rounded and 

 curved, losing the acicular character. 



In nearly all the specimens examined, bundles of acicular fibres, 

 apparently of tremolite, are scattered abundantly in the calcite. 

 The appearance of some of these is partially shown in fig. 3. 



Fig. 4 represents a specimen which, in its structure, closely resem- 

 bles the " acervuline " portion of some of the best specimens from 

 Canada. The calcite spaces show the characteristic tubuli of Eozoon, 

 and these are invariably smaller than in the specimens of coarser 

 structure. 



I have observed in this piece, also, some traces of a regular ar- 

 rangement of the serpentine granules (not well shown in the figure). 

 Several of these appear on different parts of the surface arranged in 

 regular curved lines, the granules composing each little arc being of 

 very nearly the same size and form. Curves of this kind formed by 

 four or five grains, or more, are too common to escape notice in a 

 careful examination of the polished surface. 



I notice a similar structure in a fine specimen of the eozoonal rock 

 from Canada, which I received from Dr. Hunt. 



In some portions of the rock the serpentine appears embedded in 

 the limestone in definite crystalline forms, apparently pseudomorphs 

 of chrysolite, or boltonite. In the quarries of Boxboro' and Carlisle, 

 cinnamon garnet is abundant, associated with scapolite and green 

 pyroxene or coccolite, with calcite. I have examined the calcite of 

 many of these specimens for traces of the eozoonal structure, but, so 

 far, with negative results. In fact, so far as I have observed, the 

 tubuli invariably occur in the rock associated with serpentine. 



