the Subject of "Eozcou:' 393 



4th. The " chamber-casts " being composed occasionally of 

 Loganite and malacolite (besides serpentine) is a fact which, 

 instead of favouring their organic origin as supposed, must be 

 held as a proof of their having been produced by mineral 

 agencies, inasmuch as the three silacid minerals named have 

 a close pseudomorphic relationship, and may therefore replace 

 one another. 



oth. Dr. Giimbel, observing rounded, cylindrical, and tuber- 

 culated grains of coccolite and pargasite in crystalline calci- 

 tic marbles, considered them to be " chamber-casts," or of 

 organic origin. We have shown that such grains often pre- 

 sent crystalline planes, angles, and edges — a fact clearly pro- 

 ving that they were originally aggregations of simple or 

 compound crystals that have undergone external decretion by 

 chemical or solvent action. 



6th. We have adduced evidences to show that the '^ num- 

 muline chamber-wall"* in its typical condition (that is, con- 

 sisting of cylindi'ical aciculaj separated by interspaces filled 

 with calcite) has originated directly from closely packed fibres, 

 these from chrysotile or asbestiform serpentine, this from in- 

 cipiently fibrous sei-pentine, and the latter from the same 

 mineral in its amorphous or structureless condition f. 



7th. The " nummuline wall," in its typical condition, un- 

 mistakably occurs in cracks or JissureSy both in Canadian, 

 Connemara, and other ophites \. 



8th. The " nummuline wall " is paralleled by the fibrous 

 coat which is occasionally present on the surface of grains of 

 chondrodite§. 



9th. We have shown that the relative position of two super- 

 posed acicular layers (an upper and an under '' nummuline 

 wall "), and the admitted fact of their component aciculte often 

 passing continuously and without interruption from one " cham- 

 ber-cast " to another, to the exclusion of the " intermediate 

 skeleton," are totally incompatible with the idea of the said 



* Quart. Jouni. Geol. Soc. vol. xxii. pi. xiv. fig-s. 1 & 2 ; Proceedings 

 Royal Iri^h Acad. vol. x. pi. xli. figs. I & 2. Few figures of the " cham- 

 ber-wall," published by the constructors of "Eozooti,''' afibrd a proper idea 

 of its structure. We were tlie first to represent it in its typical condition. 



t The so-called " nummuline wall " (a-sbestiform coatj in Dr. Car- 

 penter's constructed representation, hg. 2, ought not to be represented in 

 the way it is — bounded by two continuous lines — as it is an integral portion 

 of the grains and plates of serpentine (the so-called "chamber casts "J, 

 and not a chemically diHereutiated part like the true (calcareous) wall of 

 certain Foraminifers. 



I Quarterly Journal Geological Society, vol. xxii. pi. xiv. fig. 4, p. 190 ; 

 Proc. lioyal Irish Academy, vol. x. pi. xlii. figs. 5, (5. 



§ Quarterly .roumal Geological Society, vol. xxii. pi. xiv. fig?, o & (!, 

 pp. liK! & 197. 



