Tthatic Foraminifera from Somerset. 309 
lized calcite; and included in the matrix are unaltered 
remains of lamellibranch shells, echinoderm plates, &c. No 
Foraminifera were noticed in this rock. 
The third specimen is a hard shelly limestone, somewhat 
porous in texture, and composed almost entirely of the 
remains of molluscan shells. There are also some traces of 
Foraminifera, amongst which an elongate form of Ammo- 
discus, Nodosaria radicula, and Marginulina glabra (?) were 
noticed. 
In the above descriptions of the contents of the various 
washings mention has been made of the occurrence of examples 
of the genus Séacheta, hitherto known only from the Carboni- 
ferous formation, but which is here present in large numbers, 
especially in bed no. 5. On the surface of the test of this 
arenaceous foraminifer sharply defined and_ geometrically 
shaped cavities may be seen, evidently formerly occupied by 
adventitious crystals. Also,*when the cylindrical tests of 
Nodosinella are broken across, radially grouped cavities of 
prismatic form are not uncommonly seen, apparently having 
their origin in radial clusters of crystals. ‘There can, therefore, 
scarcely be any question that this organism constructed its 
test in part of these small crystals. This is the more appa- 
rent when thin slices of the tests of Nodosinella and Stacheia 
are examined ; the crystals which have left cavities are then 
seen to have been built into the minute structure of the test, 
quite unlike what one would expect to find if these crystals 
had been developed subsequently to fossilization. Professor 
Judd, who kindly examined these curious cavities in Stacheda, 
has suggested that there is great probability of the lost 
crystals having once been of the nature of small zeolites, 
such as phillipsite or christianite, a mineral which has lately 
been discovered in some abundance in the red clays and 
radiolarian oozes of the Central Pacific and Indian Oceans 
during the voyage of the ‘Challenger,’ and described by 
Drs. Murray and Renard *. 
It has been pointed out by the above authors that the 
principal reason to be adduced for the occurrence of these 
zeolitic crystals solely in deep-water deposits is that in the 
red clay the formation and deposition of the crystals are 
carried on free from the disturbing action of waves, tides, and 
currents, the stability of the waters containing the material 
in solution having thereby the opportunity to deposit the 
substance. 
* Chall. Rep., ‘Deep-sea Deposits” (1891), pp. 400-411, pl. xxii. 
rs, 1-4; woodcut (p. 402), fig. 36, 
fig 
t+ Op. eit. pp. 409, 410. 
