BRITISH DIATOMACE.E. 69 



Sowley Pond, Hampshire, Sept. 1854 ; Dunsappie Loch near Edinburgh, Aug. 

 1855, Dr. Greville. (Canal de Crapone, South of France, May 1854, W. Sm.) 



Some confusion in the specific name of the above has arisen from Professor 

 Kutzing regarding the cornute variety of E. prostratum as a distinct species, 

 whereas the modification is only an accidental variety, and occurs intermixed 

 in the same filament with the normal form ; the same modification is also 

 found in E. ceespitosum, as I have noted above, and in the gathering from the 

 South of France was quite abundant. I refer doubtfully to Kiitzing for the 

 name of the last, because his figure represents the frustule with extremities 

 slightly pointed ; still I think the same form is intended by both, and have 

 therefore ventured to adopt his name as characteristic of the habit of the 

 species, which grows in tufts, 



Plate LV. 346. 



Genus 55. COLLETONEMA, Breb. 



Frond simple or divided, filiform or globose ; frustules sigmoid or 

 direct, naviculoid ; files containing one or more rows of scattered 

 frustules. (All the species aquatic.) 



The freshwater habitat and slightly divided frond distinguish the 

 present genus from Schizonema, with which it has been confounded : 

 the frustules of Colletonema are also more firmly siliceous than those 

 of the former genus, and the character of the valve can usually be 

 well seen after maceration in acid. 



It is possible that Pinnularia radiosa may be merely the free state 

 of Colletonema neglectum, and Navicula crassinervia the same condi- 

 tion of Colletonema vulgare : if future observation confirm this suppo- 

 sition, the species of the present genus must supplant those formerly 

 described, and the latter be cancelled in a future edition of the pre- 

 sent work. 



1. Colletonema eximium, Thw. Frond filiform, more or less ab- 

 ruptly acuminate, slightly rugulose, containing one or more rows 

 of somewhat scattered frustules ; V. sigmoid, extremities rounded, 

 striated; striae 56 in -001". Length of frustule -0025" to -0034". 

 Breadth of V. -0005". v.v. 



Thw. Ann. ser. 2. vol. 1. pi. xii. F. 



Fresh or brackish water. Bristol, Dec. 1847, Mr. Thwaites. Near Lewes, 

 Sept. 1851. The Fleet, Dorsetshire, Sept. 1854, W. Sm. 



Plate LVI. 350. 



