BRITISH DIATOMACE.,E. 57 



and yet he gives as synonyms Conferva nummuloides, Eng. Bot. tab. 2287, 

 and Fragilaria nummuloides, Lyng. Tent. tab. 63, both of which species are 

 referred by most authors to our first species, and the figures of which are 

 certainly more accordant with that than with our M. Borrerii. The words in 

 the Conspectus, "articulis circularibus," are also inapplicable to the specimens 

 from Shoreham, and are correctly descriptive of our M. nummuloides. It 

 is probable, therefore, that Agardh was unable with his instrument to discri- 

 minate between these forms, and assigned them in different states to different 

 species. In uncertainty, I adopt the name of M. Borrerii, under which, in 

 honour of an excellent native observer, the species was first described in 

 Britain, and whose discovery of it in Shoreham Harbour appears to have 

 been almost simultaneous with the determination of Agardh' s M. nummuloides, 

 and venture to hope that the description and figures now given will prevent 

 future misunderstanding. The sporangia of M. Borrerii are of great size, 

 and when in this state its filaments run no risk of being confounded with any 

 of its allies. 



Plate L. 330. 



3. Melosira subflexilis, Kutz. Frustules at first cylindrical, fre- 

 quently united by a mucus-cushion, geminate ; mature and sporan- 

 gial frustules subglobular ; young valves cylindrical, with a slight 

 constriction between the apex and suture ; mature valves sub- 

 hemispherical ; extremities of valves always convex. Breadth of fila- 

 ment -0002" to -0008". Breadth of sporangial filament -001 1". v.v. 



Kiitz. Bacill. ii. 13. Raben. Siissw. Diat. ii. Conferva lineata, Dillw. Conf. 

 tab. B. Lyng. Tent, lxiii. B. 



Fresh or brackish water. Wareham, Dorset, Nov. 1849 ; Lewes, Sussex, 

 December 1851, March 1852 ; Denton, Sussex, November 1853, W.Sm. Car- 

 rickfergus, September 1853 ; Largs, July 1854, Br. Arnott. Aberdeenshire, 

 June 1848, Dr. Dickie. 



Plate LI. 331. 



4. Melosira varians, Ag. Ordinary frustules cylindrical ; sporan- 

 gial at first globular, at length cylindrical ; valves cylindrical, 

 with truncated extremities. Breadth of filament '0002" to '0011". 

 Breadth of sporangial filament '0015". v.v. 



Ag. Consp. p. 64. ad specim. authen. in Herb. Grev. Rail's, Ann. vol. 12. 

 pi. ix. 5. ad specim. in Herb. Jenn. Kutz. Bacill. ii. 10. ad specim. quae 

 misit am; De Brebisson. Hass. Alg. xciii. 4 & 5. Thw. Ann. 2nd ser. 

 vol. 1 . pi. xi. A. Prit. Anim. xxiv. 32. Gallionella varians, Ehr. Inf. x. 4. 

 Confervafasciata, Dillw. Conf. tab. B. 



Freshwater: very frequent. Winterboume, Lewes, April 1852. Itford, 



