PBOGRESS OF MICROSCOPICAL SCIENCE. 99 



Bathyhius. Mr. Carter says, considering tliat the coccolitli is so abun- 

 dant in the Laminarian zone, and so voraciously fed on by the Echino- 

 dermata and AscidijB, also that it is so nearly allied to Melohesia 

 calcarea, that it forms the bed of the Atlantic and is found fossilized 

 in the chalk, he cannot help inferring that it is a vegetable organism 

 which contributes chiefly to form the calcareous deposits of the present 

 day as it has done in the past, at all events in the chalk. 



A Mineral Silicate injecting PalcBozoic Crinoids. — Dr. T. Sterry Hunt, 

 F.E.S., states that a Silurian limestone from near Woodstock, New 

 Brunswick, lately examined microscopically by Dr. Dawson, was found 

 by him to consist almost wholly of comminuted organic remains, in- 

 cluding fragments of trilobites, gasteropods, brachiopods, and joints of 

 small encrinal stems and plates ; the whole cemented by calcareous 

 spar in a manner similar to many organic limestones. He observed, 

 however, that the pores of the crinoidal remains were injected by a 

 peculiar mineral, readily distinguishable in thin transparent sections, 

 or on surfaces which had been exposed to the action of an acid, which 

 dissolves the carbonate of lime and places in relief the injecting mine- 

 ral. The minute structure thus revealed is precisely similar to that 

 of recent crinoids studied by Carpenter, and will soon be described and 

 figured by Dawson. Decalciiied specimens exhibit a congeries of 

 curved, branching and anastomosing cylindrical rods of the replacing 

 mineral, sometimes forming a comj)lex network, which under the mi- 

 croscope resemble the coralloidal forms of aragonite known as Jlos 

 ferri, and present a frosted crystalline surface. The same mineral, as 

 observed by Dr. Dawson, occasionally occupies larger interstices among 

 the fragments, and was evidently deposited before the calcareous spar 

 which cements the whole mass. When this limestone is dissolved in 

 dilute hydrochloric acid, the residue, washed by decantatiou, equals 

 from five to six per cent, of the weight of the mass, and is seen under 

 a microscope to consist entirely of the casts composed of the mineral 

 just noticed, mixed with about one-fourth of coarse silicious sand. This 

 matter is pale greyish green in colour, but when calcined becomes of 

 a bright reddish brown, without change of form. Heated in a close 

 tube it gives off water, and becomes much darker in colour. It is 

 partially attacked by strong hydrochloric acid, which takes up much 

 protoxide of iron ; but is readily and completely decomposed by hot 

 concentrated suli^hvuic acid, leaving a skeleton of silica which, by a 

 dilute solution of soda, is readily separated from the intermingled 

 grains, more or less rounded, of colourless vitreous quartz. 



TJie Mineralogy of Eozoon. — It is stated in ' Silliman's American 

 Journal,' in a note, we think, by Professor Sterry Hunt, that Dr. Eobert 

 Hoffmann, of Prague, has submitted to chemical and mineralogical 

 investigation the Eozoon Canadense, found at Easpenau in Bohemia.* 

 He describes the Eozoon mass as having a suiJerficial resemblance to 

 that of Canada, appearing in waved or concentric bands, oval in form, 

 or else in irregular acervuline aggregates. In the oval banded 

 portion the shell of the Eozoon, a nearly pure, finely granular calcite, 



* ' Jour, fur prakt. Cbemie,' May, 1869. 



