56 BRITISH DIATOMACE^E. 



Marine, or brackish water: frequent. Poole Bay, June 1848; Seaford, 

 Sussex, May 1850; Bexhill, Sussex, Oct. 1852; Belfast Bay, July 1853; 

 Cork Harbour, April 1855, &c, W.Sm. Kinghorn, Fife, Nov. 1853, Dr. 

 Greville. Newbie Deposit, Prof. Harkness. Var./3. Itford, Sussex, March 1853; 

 Newhaven, Sussex, Nov. 1853. Var. y. Seaford, Sussex, April 1854, W. Sm. 



The synonymy of this genus is much confused, and without authentic 

 specimens, it is impossible to determine species from the description or figures 

 of authors. I believe that all the above forms are to be referred to a single 

 species, which is pretty constant in every locality in which it has occurred to 

 me. The only differences I have noticed, consist in the greater or less de- 

 velopment of the connecting mucus-cushion, and the presence or absence of 

 the curious keel-like rim of silex : — forms aberrant in these respects are, how- 

 ever, so frequently intermixed with the ordinary frustules, that I cannot regard 

 such peculiarities as of specific importance. 



All filamentous species of Diatomacese being probably stipitate on their first 

 production, the free or attached condition of the Melosirece cannot be regarded 

 as even constituting varieties, and the M. salina ft. of Kiitzing must there- 

 fore be discarded. 



Plate XLIX. 329. 



2. Melosira Borrerii, Grev. Ordinary and sporangial frustules 

 subcylindrical, all geminate ; polar usually much shorter than the 

 equatorial diameter ; valves subhemispherical, distinctly cellulate ; 

 cingulum marked with conspicuous circles of cellules. Breadth of 

 ordinary filament '001 1" to '0022". Breadth of sporangial filament 

 •0031" to -0052". v.v. 



Var. ft. Filaments very much curled. 



Grev. B. F. p. 401. Ralfs, Ann. vol. 12. pi. ix. 2. ad specim. authen. in herb. 

 Jenn. Thw. Ann. 2nd ser. vol. i. pi. xi. C. Gallionella lineata, Ehr. 

 Inf. x. 2 C? Melosira moniliformis, Kiitz. Bacill. hi. 2. ad specim. qiue 

 dedit cl. De Brebisson. Melosira nummuloides, Ag. Consp. p. 65. ad 

 specim. authen. in Herb. Grev. 



Marine, or brackish water. Poole Bay, in great abundance, Nov. 1848 and 

 March 1852 ; Coast of Sussex, Dec. 1851 and Feb. 1852, W. Sm. Aberdeen, 

 June 1848, Dr. Dickie. Belfast Bay, Sept. 1853, and Frith of Clyde, July 

 1854, Dr. Arnott. Var. ft. Near Lewes, Feb. 1852, W. Sm. 



This species is readily distinguished from the last by its larger size, and 

 the globular and more cylindrical form of its frustules. Its cellulate structure, 

 which gives a rich brown hue to the desiccated filament, also affords an easy 

 means of identification. It would appear, from a note in the ' Conspectus,' 

 that Agardh regarded this species as identical with his Melosira nummuloides ; 

 tor he says, — " Specimina ex Shoreham Harbour mihi a Borrero communi- 

 cata omnino conveniunt cum specirninibus, quae ipse cum Hoffmanno legi ;" 



