i895- EOZOON AND THE MONTE SOMNA BLOCKS. 401 



observed which I have no doubt would be farther accentuated by 

 comparison of actual specimens. 



I have already referred to the apparent inversion of acervuline 

 and laminated structures ; but there is a more important difference 

 than this, at least, in several of the figures. The Vesuvian specimens, 

 as shown therein, consist of continuous laminae of crystalline igneous 

 matter, including interrupted or lenticular layers of calcite. Eozoon, 

 on the contrary, when well preserved, consists of a continuous 

 skeleton of calcite composed of broad layers slightly pitted on their 

 surfaces, and connected at intervals ; while the silicious material 

 appears as a substance filling wide, flattened, mammillated chambers, 

 more or less limited, and presenting amoeboid lobes at their extreme 

 edges, and passing finally, in the upper part, into rounded chamber- 

 lets. This difference should commend itself to any palaeontologist ; 

 but I am aware that it may be overlooked by cursory observers. 

 Scores of specimens have been sent to me of banded rocks, supposed 

 by their finders to resemble Eozoon, though, in arrangement of parts, 

 the converse of it. 



The authors of the paper seem to have peculiar ideas respecting 

 even the general form of Eozoon. I have repeatedly shown, and have 

 illustrated this by photographs, that when we find perfect detached 

 individuals of Eozoon, these are usually of inverted conical form, 

 springing from a narrow base and widening upward in the manner of 

 some sponges and corals. When close together they often become 

 confluent, and when these confluent masses or layers appear to be 

 hollow or doubled, I believe that this usually results from the folding 

 of the containing bed. This can, indeed, often be seen to be the case, 

 and the laminae may be observed to be bent and crushed at the 

 flexures. 



In the specimens figured in the paper, the characteristic micro- 

 scopic structures of Eozoon are entirely absent. There is no trace of 

 the beautiful and complicated system of canals, and the fibrous 

 structures compared with the minute tubulation are merely prismatic 

 fibrous crystals like the secondary veins of chrysotile which sometimes 

 cross and deteriorate our specimens of Eozoon. With reference to 

 these chrysotile veins, while their filling of minute and often transverse 

 and branching cracks show that they are merely aqueous deposits of 

 later origin than the structures which they traverse, and while their 

 appearance under high powers is very different from that of the tubuli 

 of the calcite layers, they have no doubt been when parallel to the 

 layers, and in poor specimens, fertile causes of error. Fortunately, 

 however, they are absent from the more perfect specimens. I may 

 also explain that while the finely tubulated margin of the calcareous 

 layers can be seen to terminate abruptly against the filling of the 

 chambers, it passes gradually in the interior of the layer into the 

 larger canals when these are present. Naturally also, the finely 

 tubulated wall often fails to show its structure, just as anyone who has 



