Mr. J. Ralfs on the British Diatomacese. Ill 



gated (eight to twelve times longer than broad), not striated ; the 

 front view is narrow linear-lanceolate with truncate ends, and 

 the lateral surfaces, which are about the same breadth, are lan- 

 ceolate with subacute extremities. 



The colouring matter occupies only the central third of the 

 frustule, and consequently the ends are hyaline. 



Platk III. fig. 2. Berkeleya fragilis : a, front view; h, lateral view, 



Encyonema, Kiitz. 



Frustules cymbiform, siliceous, arranged in longitudinal series 

 within submembranaceous, tubular filaments. 



The filaments are tubular, submembranaceous, and under the 

 microscope colourless. The lateral surfaces of the frustules being 

 convex are observed in the front view, in which also the frustules 

 are quadrilateral with two puncta at each end. These puncta are 

 less easily discerned in the dorsal view as the dorsum is longi- 

 tudinalty convex. The lateral view is semi-elliptic with numerous 

 transverse strise, which are interrupted as in Cocconema by a lon- 

 gitudinal pellucid line. 



This genus difiers from Schizonema and other frondose genera 

 of DiatomacecB in the form of its frustules, as a single frustule 

 resembles one of Cymbella or Cocconema ; therefore, notwithstand- 

 ing the similarity of habit, it belongs to a difi*erent series. 



It is far more probable that some bodies of a totally different 

 kind will be at first sight classed with Encyonema. These, which 

 are really congeries of the ova of certain insects, were once de- 

 scribed by Agardh as Algae under the name of Gloionema. A 

 little attention however will secure the observer from this mistake, 

 for although cymbiform and arranged in longitudinal series, the 

 eggs are neither siliceous nor striated. 



1. E. prostratum, Berk. Kiitz. Die Kieselschalig en Bacillaria oder 

 Diatomeen, p, 82. t. 25. f. 7. E.paradoxum, Kiitz. Synop. Diatom, 

 in Linnaea 1833, p. 589. f. 73; Die Kies. t. 22. f. 1. Monema 

 prostratum. Berk. Br. Alg. p. 15. t. 4. f. 3. (1832) ! Schizonema 

 prostratum, Grev. in Hook. Br. Fl. vol. ii. p. 414 ; Harv. Br. Alg. 

 p. 214. Gloionema paradoxum, Ehr. Inf. p. 237 (not of Agardh 

 nor Kiitzing) ; Portlock in Microscop. Journ. vol. ii. p. 6. pi. 3. 

 fig. 1. 

 In freshwater rivulets, outlets of ponds, &c. near King's Cliffe, 



Northamptonshire, Rev. M. J. Berkeley ; Farnham, Surrey, Mr. W. 



Reeves; Brambletye, Sussex, and "abundant in the rivulet which 



parts Kent and Sussex between Bodiham and Sandhurst," Mr.Jenner; 



near Bristol, Mr. Thwaites. Ilfracombe, Devonshire, /. R. ; "Lough 



Erne, Ireland, Capt. Portlock." 



This plant forms small tufts, which not unfrequently are so 



