4 PRELIMINARY NOTICES. 



Jenn. F. Tun. Flora of Tvmbridge Wells. ByE. Jenner, A.L.S. (no date). 

 Kiltz. Bacill. Die Kieselschaligen Bacillarien, von F. T. Kiitzing, 1844. 

 Kiitz. Phy. Ger. Phycologia Germanica, von F. T. Kiitzing, 1845. 

 Kilfz. Sj). Alg. Species Algarum, von F. T. Kiitzing, 1849. 

 Lync/. Tent. Tentamen Hydrophytologise Danicse. H. C. Lyngbye. 2 vols., 



1819. 

 Prit. Anim. A History of Infusorial Animalcules. By A. Pritchard, M.R.I., 



1852. 



Quek. H. C. Histological Catalogue of the College of Surgeons. By 

 J. Quekett. 



Ralfs, Ann. Papers in the Annals of Natural History. By J. Ralfs, 

 M.R.C.S., v.d. 



W. Sm. Ann. Papers in ditto. By Rev. "W. Smith, F.L.S., v. d. 



Thio. Ann. Papers in ditto. By G. H. K. Thwaites, v. d. 



The letters n. sp. denote that the species to which they are appended is 

 believed to be now for the first time described : W. Sm. that the species has 

 been previously described, or the generic or specific name been altered, by the 

 present writer ; in the latter case the original appellation is given in the list of 

 synonyms. In other cases the writers by whom generic and specific names 

 have been first employed are indicated by contractions, the signification of 

 which may generally be ascertained by a reference to the list of authors 

 given above. 



The following abbreviations are adopted in the text : — 



F. = Frustule. 

 F. V. = Front view of frustule. 

 S. V. = Side view of frustule. 



V.= Valve. 



l"=English inch. 



The letters S. V. and V. may usually be employed indifferently, as in most 

 cases the outline of one valve, when its general surface is turned towards the 

 observer, is identical with that of the side view of the entire frustule. 



The letters v. v. following the specific description imply that I have examined 

 a living specimen, and v.s. that I have seen the species only in a dry or 

 fossil state. 



The letters which accompany the numbers in the Plates indicate that the 

 figures to which they are attached represent, — a, a side view ; b, a front 

 \'iew ; c, a front view of single valve ; and d, self-division : when a numeral 

 alone is employed, the figure is that of a side view of a single valve. 



The unit of measurement employed is that of an English inch, the magni- 

 tudes being expressed in decimals, thvxs enabling those who may desire to 

 reduce the dimensions given to the various continental standards (when the 

 values of these are known), to do so by a simple process. The scale in each 



