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



There are among these, two new forms of Infusoria ; but besides and 

 accompanying them, silicious parts of phanerogamous plants, probably 

 grasses, and of Equisetacece, are worth remarking. It would seem pro- 

 per to distinguish such fragments with generic names in separate lists, 

 in order they should not be disregarded ; since it is not easy to deter- 

 mine to what plants they might belong. The silicious, marginal serra- 

 tures of grasses are found plentifully under the silicious shields of the 

 Infusoria. These will be named Lithodontium (Thylacium). The serra- 

 ted, silicious fibres of the elongated cells of grasses, which are not 

 immediately the epidermis, will be named Lithostylidium, and the sili- 

 cious epidermis of the Equisetacece, Lithodermatium. 



By this means, such botanical forms, which are frequently very dis- 

 tinct and characteristic, and hitherto unremarked, can be retained and 

 compared by the microscope, without loading systematic Botany with 

 misapplied names, by groundless guesses at their origin. 



From Peru, besides the five species of marine Infusoria already noticed, 

 as yet only four, from the interior are known, viz. : Eunotia Zebra, 

 Fragilaria ?, Navicula viridis, Spongilla lacustris, of which no form can 

 with certainty be indicated as new. 



The addition to the fauna of Iceland, afforded by the materials col- 

 lected by Dr. Thienemann is especially interesting. He has furnished 

 marine Conferva? from the coast, and peat from Husavic. The peat is 

 very rich in silicious Infusoria, although it is a good, in fact the best, 

 combustible material in the island. It contains not fewer than the fol- 

 lowing thirty- six species : 



1. Amphiprora navicularis. 16. Gallionella distans. 



2. Amphora libyca. 17. crenulata. 



3. hyalina. 18. Gomphonema acuminatum. 



4. Arcella hyalina. 19. Americanum. 



*5. Coccone'is borealis. 20. longiceps. 



*6. longa. 21. truncatum. 



7. Cocconema asperum. 22. Navicula amphioxys. 



8. Eunotia amphioxys. *23. cequaUs. 



9 bidens. 24. amphisb&na. 



10. Diodon. 25. gastrum. 



11. - granulata. 26. - - leyumen. 



12. gibba. *27. liostauron. 



13. prterupta. 28. microstauron. 



14. - Zebrina. 29. - - nobilis. 



15. Fragilaria striolata ? 30. phccniccnteron. 



