304 Mr, Weaver*s View of Ehrenherg's Observations 



has been advanced will suffice to show clearly tlie position of the 

 Polythalamia, such as it appears to me, in the animal kingdom." 



On Chalk and Chalk Marl. 



The memoir on the chalk and chalk marl is distributed 

 under the following heads : — 



1. Historical Introduction, pp. 59 — 68. 



2. New method of observing, pp. 68 — 70. 



3. On calcareous-shelled organisms, invisible to the naked 

 eye, as the principal constituents of writing chalk, pp. 70 — 74. 



4. On Chalk Marl and its relations to Chalk, and to the 

 Flints of the Chalk, pp. 74—87. 



5. On the compact limestone of Upper Egypt and Arabia, 

 as formed by the Polythalamian calcareous animalcules of the 

 White Chalk of Europe, pp. 87 — 90. 



6. On the principal organic calcareous forms which con- 

 stitute all chalk, and the local differences, pp. 90 — 95. 



7. Preliminary view of new researches respecting living 

 Polythalamia, and their relation to the formation of the sand 

 of Sea Downs, pp. 96—106. 



8. Application of the preceding observations to the system- 

 atic distinctions of Polythalamia, with a tabular view of the 

 Bryozoa, according to their orders, families and genera, with 

 their characteristics, pp. 107 — 121. 



(N.B. Of this tabular view I have given a transcript above.) 



9. On the geographical distribution of living Polythalamia 

 on the African and Asiatic coasts of the Mediterranean, and 

 in the Red Sea, with a tabular view of the genera and species, 

 pp. 121—127. 



10. A concise Diagnosis of the new families, genera and 

 species, 



1. Of the siliceous Infusoria of the chalk marl, con- 



taining thirty-one new species, of which seventeen 

 species belong to five new genera, and fourteen 

 species to five former-known genera, pp. 128 — 130. 



2. Of the calcareous-shelled Polythalamian animalcules 



of the chalk and sea sand, sixty-seven new species, 

 beside two new species from the Jura (Oolite) lime- 

 stone, pp. 130—135. 



11. A summary view of the conclusions drawn from the 

 preceding expositions, pp. 135 — 139. 



12. Explanation of the Plates, pp. 140 — 147. 



13. A tabular view of the organic bodies invisible to the 

 naked eye, which form the chief constituents of chalk, chalk 

 marl, the compact limestone of Egypt and Arabia, and the 

 nummulitic limestone of the Pyramids of Geza or Gyzeh. 



