152 
PROF. T. RUPERT JONES-ORIGIN AND 
Small Serpulce, Ostrece, Brachiopoda , etc. 
Fragments of shells, especially prisms of Inoceramns. 
Ossicles of Crinoids. 
Spines, plates, and fragments of Echinoids. 
Ostracoda (abundant). 
Foraminifera (abundant), and Eadiolaria {Polycystina : rare). 
Skeletal fragments and spicules of Sponges. 
If examined with, high magnifying powers, 
Coccolitbs, and in some cases Rhabdoliths. 
Diatomacese have been recorded by Ebrenberg as found in the Chalk of 
Gravesend, namely Fragilaria rhabdosoma and Fr. ( striolata) pinnata. 
See ‘ Ann. and Mag. Nat. Hist.,’ ser. 4, vol. ix, p. 301. 
In the foregoing list the majority are calcareous organisms, or 
rather they have calcareous shells or other structures made of carbo¬ 
nate of lime, which they take in with their food and leave as solid 
material when they die. Most of the sponges, however, have 
siliceous skeletons or spicules; the Polycystina have a siliceous 
framework ; and the minute diatomaceous Algse, of course, have 
siliceous frustrules. Of the last, the known evidence is very scanty. 
Of Polycystina , however, Dr. Wallich has discovered Astromma, 
JEalliomma , and Podocyrtis, also some of the allied PietyochidceP 
Previously I had known of only one specimen (in the Dev. H. Eley’s 
collection); but Professor Zittel had noticed some in the Chalk of 
Germany. There is no doubt that both Diatoms and Polycystines 
live freely floating in the water, and their skeletons therefore have 
fallen down to the bottom to become with others a portion of the 
sea-bed. Of the spicules of Sponges some notice has already been 
taken (page 150). A list of the Ostracoda of the Chalk and 
associated strata, revised in 1870, is given in the ‘Geological 
Magazine,’f and those found by Mr. Joseph Wright in the Antrim 
Chalk (some of them new species) are enumerated in the 
‘ Proceedings of the Belfast Naturalists’ Field Club.’J 
Some notes on and a list of the Foraminifera known from the 
English Chalk and Chalk-marl are published in my ‘ Catalogue of 
the Fossil Foraminifera in the British Museum.’§ Those belonging 
to the two formations are sufficiently distinguished; and those from 
the Chalk of Antrim are given in a separate list. || Of the Crusta¬ 
cean and Bhizopodal groups of these Microzoa a brief account was 
given by me in a lecture before this Society in November, 1882.^[ 
which need not be repeated here; but a few words on the Fora¬ 
minifera, as to the relationship of those now living in the 
Atlantic, and other deep seas, with the Chalk, may be acceptable. 
In the masterly ‘Deport on the Foraminifera dredged by H.M.S. 
“Challenger”’ [and other expeditions], by H. B. Brady, Esq, 
F.D.S.,* * * § ** we have the results of his long-continued and enlightened 
* In flint from Surrey. See 1 Ann. and Mag. Nat. Hist.,’ July, 1883, p. 52. 
t Yol. vii, p. 74, etc. 
f New ser., vol. i, 1875, Appendix, p. 81 and p. 92. 
§ 8vo. 1882, pp. 85-88. || pp. 88-90. 
IF ‘Trans. Herts Nat. Hist. Soc.,’ Yol. II, pp. 169-171. 
** 2 vols. 4to. 1884. 
