208 PKOCEEDINGS OF THE GEOIOGICAI SOCIETY. [Jan. 10, 



nected with another to the left by an elongated neck-like constriction 

 composed of their own substance — serpentine. 



Undoubtedly there also occur bodies having no relation to either 

 the " definite shapes" or the " chamber-casts." We, too, have seen 

 examples in Grenville Ophite " of a mode of communication, of the 

 chambers when they are completely separated, which," in certain 

 aspects, appears to " have its exact parallel in Cydoclypeus :" it con- 

 sists of thickish, pale-grey, translucent, parallel-sided pieces, with 

 a subdued silky lustre, stretching across the decalcified passages, and 

 connecting opposite " chamber-casts," as in PL XIV. fig. 10, magnified 

 105 diameters. When these pieces were first detected, we had no 

 doubt whatever of their being true " casts of stolon-passages ;" but 

 afterwards, on a rigid reexamination, we found every one of them to 

 be nothing more than a flattened or table-shaped crystal of what 

 appears to be pyrosclerite* placed edgeways or perpendicular to the 

 plane of section, and wedged in between two granules. The total 

 distinctiveness of the former from the latter, a circumstance incon- 

 sistent with their being " casts of stolon-passages," is unmistakeably 

 marked by their colour, lustre, and well-defined terminations. It 

 thus becomes evident that the position of these crystals had misled 

 us (and we may be allowed to suggest this to have been the case 

 with other investigators), and that certain of the "narrow passages " 

 which have been regarded as '' exactly corresponding to those in 

 Cydoclypeus " are not so ; for instead of being cylindrical, like the 

 " canals" represented in figures of this foraminifer, they are broad, 

 flat, and parallel-sided. In numerous instances the crystals of pyro- 

 sclerite extend only partially across the passages, "forming mere 

 tongues," which have been misconceived to " represent correspond- 

 ing extensions of the sarcode-body "t. When two or more crystals 

 are associated and lie parallel to one another, or when a single 

 crystal is divided, by cleavage -partings, we are strongly reminded of 

 the example represented in the ' Quarterly Journal of the Geological 

 Society,' vol. xxi. pi. vii. fig. 2. In some eases, a " white amorphous 

 mass," rudely laminated, as in PI. XIY. fig. 11,^ magnified 105 dia- 

 meters, is interposed between a crystal and a granule, linking^the two 

 together. 



We ha^e also seen similarly flattened crystals fixed in the calcite 

 of incompletely decalcified passages. Crystals of the same mineral, 

 .x}ccurring under precisely similar circumstances, characterize the 

 Ophite from Glanochan and other Connemara localities ; also nume- 

 rous tabular crystals of mica. Crystals of chlorite, occupying the 

 same situation, occur numerously in the Indian Ophite. 



* Pyrosclerite or white chlorite, a hydrous silicate of magnesia and alumina, 

 occvirs both amorphous and crystallized, Dana describes it as " hexagonal(?)," 

 and having a " perfect basal cleavage." The crystals noticed in the text might 

 be considered to be modified rhombic tables : they are translucent, of a pale 

 greenish colour, have a weak lustre, and show a transverse lamellar cleavage. 

 We took them at first for crystals of some kind of mica ; but their lustre is not 

 sufficiently glistening. Amorphous pyrosclerite, in large lumps, occurs near the 

 Barna-Oran Ophite-quarry (Connemara). This variety was analyzed by one of 

 us a few years ago. (See British Association Eeport for 1860, Sect. pp. 71, 72.) 



t Carpenter, Quart. Journ. Gfeol. Soc. vol. xxi. p. 62. 



