NARRATIVE OF THE CRUISE. 
557 
point of the Tionfolokker Islands, were the richest in new species and number of speci- 
mens obtained during the cruise, siliceous Sponges, Corals, Pennatulids, and Echinoderms 
being especially abundant. 
The deposit at this Station was also of considerable interest. The sounding tube 
brought up specimens of a blue mud, containing about 10 per cent, of carbonate of 
lime, and in the trawls, besides pumice stones, were several large concretions or 
fragments of a calcareous rock, differing very considerably from the deposit. 
The Concretions were of two kinds. First, many more or less rounded agglutinations 
loosely held together, and from 1 to 7 centimetres in diameter. Second, several large 
honeycombed pieces of rock, several decimetres in diameter, and requiring a sharp blow 
from a hammer to break them. 
Those belonging to the first variety are grey or brown, sometimes slightly greenish, 
granular, and it can be seen with the lens that they are essentially composed of 
Foraminifera. An examination of thin sections of these nodules shows that they are 
agglutinated, or coagulated by an argillo-ealcareous cement which is not in great 
abundance. Some of the shells are entirely filled with pale green glauconite, others 
only partially. The intervals between the shells are not filled up with the cementing- 
matter, and appear to be the first phase of agglutination. 
Those of the second variety are very irregular in shape, and consist of large pieces of 
a hard rock traversed in all directions by large and small perforations, with a diameter 
varying from 1 to 4 centimetres. These blocks have thus a cavernous or coarse cellular 
appearance. The perforations are covered, like the surface of the rock, with organisms, as 
Sponges, Polyzoa, &c., and rough to the touch ; the smaller perforations have sometimes 
the appearance of having been produced by litliophagous Molluscs. These concretions 
have the hardness of ealcite ; the freshly broken fragments are white-grey. A microscopic 
examination shows that they are mainly composed of various species of pelagic Foramini- 
fera. Treated with weak acid the concretions decompose with effervescence, leaving a. 
residue of 20 '44 per cent., the rest being carbonate of lime. The residue is essentially 
composed of argillaceous matter, together with a few grains of felspar and quartz, and 
glauconitic casts of the Foraminifera, these last being brown or green and feebly 
transparent. The greenish casts present most of the characters of true glauconite. 
Examined with the microscope in thin sections, the Foraminifera composing the rock 
are seen to be the same as those in the first variety and also in the muds of the 
same region ; mixed up with these are fragments of Echinoderms, &c. They are some- 
times filled with greenish glauconite, but more generally with a semi-opaque greyish 
matter which constitutes the cement of the various elements of the rock, and must be 
considered as impure carbonate of lime. It has a slightly opaline aspect, is homogeneous 
under low powers, but with higher powers a fine granulation can be seen which the 
