519 



some localities in Canada, is not general even there (" The acervuline 

 portions make up a large part of the Canadian specimens of Eozoon," 

 Sterry Hunt*) ; and it is extremely rare in other countries. We have 

 met with only a few specimens from Connemara offering an approach 

 to it ; while all those we have examined, collected on the Continent, 

 have the " chamber casts," with an acervuline arrangement : besides, 

 the specimens described by Dr. Giimbel " show throughout this irre- 

 gular structure, which seems to characterize the Bavarian specimens;"! 

 and those collected at Krumau in Bohemia, by Professor Hochstetter, 

 are essentially acervuline. In describing any organism having a wide 

 geographical range, no naturalist would consider that plan of growth 

 which marked it in only one locality (or which may be only beautifully 

 exhibited in a few museum or cabinet specimens, selected out of a large 

 number in a different condition on account of possessing such feature) to 

 be general or " typical" Rather, would he consider it to be exceptional. J 

 One of the many interesting points connected with " eozoonai" 

 ophite is, that the granules or " chamber casts" may consist of different 

 species or varieties of mineral silicates, serpentine and diopside (or mala- 

 colite) being common. In one place a specimen may have the layers of gra- 

 nules formed entirely of the former, and in another of the latter. " Some 

 sections exhibit these two minerals filling adjacent cells, or even por- 

 tions of the same cell, a clear line of division being visible between 

 them" (Hunt). In one of the sections presented to us by Dr. Car- 

 penter there occurs a layer of granules, apparently consisting of chon- 

 drodite, lying between others of serpentine. Loganite is another mi- 

 neral which often replaces the latter. Connemara ophite occasionally 

 displays precisely the same differences. In a specimen before us, a 

 layer, composed of granules of serpentine, lies immediately adjacent 

 to another, formed of an aggregation of crystals of what appears to be 

 malacolite intermingled with calcite. Another specimen consists of pa- 

 rallel layers, varying from a quarter to an inch in thickness, of granular 

 serpentine, (?) pyrallolite, openly cleaved malacolite, and a guttate wax- 

 like mineral (? deweylite). Calcite, which is more or less associated with 

 all these minerals, fills up the cleavage openings of the malacolite ; demon- 

 strating that in the latter the silicate has undergone partial removal, and 

 that the resulting openings have become filled in with a carbonate. 



Long ago Dr. M'Culloch directed attention to the different silicates 

 occurring in the green-spotted pink marble of Tyree;§ and his state- 



* " Canadian Naturalist," December, 1866, p. 90. 

 t Ibid. 



% Dr. Dawson has charged us with the admission that the " laminated forms are 

 essentially Canadian." What is stated in our Paper is— " we had got the impression 

 that in the Grenville varieties the chamber casts were rarely arranged otherwise than in 

 laminae ;" but after examining some specimens presented to us by Sir W. E. Logan, "we 

 saw that the acervuline arrangement was a characteristic feature of the Canadian ophite 

 ("Quarterly Journal of Geological Society," vol. xxii., p.190). 



§ " Western Highlands of Scotland," vol. i., p. 54, &c. 



It. 1. A. PEOC — VOL. X. 1 



