ON THE FILLING UP OF RIVER-BEDS AND HARBOURS. 133 



countries, the following results, as to the extent of animalcular life have 

 been obtained." 



In the Malvinas or Falkland Islands the following 30 species of mi- 

 croscopic organisms still exist ; 



1. Achnanthes pachypus 17. Grammatophora oceanica. 



2. Actinocyclus senarius. *18. stricta. 



*3. Amphora navicularis. 19. Navicula amphioxys. 



*4. Arthrodesmus Taenia. 20. aspera. 



5. Cocconeis placentula. 21. Didymus? 



6. scutellum. *22. Lyra. 



7. Cocconema Lunula ? *23. peregrina. 



8. Eunotia Faba. 24. viridis. 



9. amphioxys. *25. Surirella? australis. 



1 0. biceps. 



11. Fragilaria constrict a. 26. Spongia acicularis. 



12. rhabdosoma. 27. capitata. 



*13. Trachea. 28. Clavus. 



14. Ventriculus. 29. 



15. Gomphonema clavatum. 30. aspera. 



16. minutissimum. 



Out of all this number of forms, there are only seven new species, (*) 

 which had not already been met with elsewhere. As a whole the forms 

 belong to already known genera. Most of them are as yet only known 

 as marine, and from this, it may with greater probability be concluded, 

 that the whole of them are so. Several species belong to those, which 

 assist in the formation of the chalk marl in the south of Europe. 



For the Brazils, twelve still living species, from alluvial deposits are 

 added to the nine already stated to have been met with in the edible 

 clay of the Amazons, furnished by M. Martius, viz : 



*1. Arcellaecornis. 8. Synedra Ulna. 



2. Gallionella distans ? 



3. Himantidium Arcus. 9. Lithodontium Bursa. 



4. Navicula viridis. 10. Lithostylidium Serra. 



5. amphioxys. *11. articulatum. 



*6. microstauron. *12. Lithodermatium macrodon. 



7. Surirella oblonga ? 



* The new species, which as far as is yet known are characteristic of the countries, 

 are marked with an asterisk. 



