BRITISH DIATOMACEiE. 45 



its valvular inflations of equal size, and the other having the central 

 inflation larger than the terminal enlargements. I cannot accept any 

 of these characters as a sufficient specific distinction. In all the 

 specimens I have examined, and it will be seen how widely these 

 have been collected, I find alternate septa. The alternate character 

 is distinctly obvious to the eye in T.flocculosa ; but that their position 

 and character are precisely similar in T. fenestrata, must I think be 

 apparent by an examination of the analyses given in Plate XLIII. 

 316f & 31 7i" ; in both, the septa are confined to one extremity of 

 each annulus, and must therefore in both be really alternate. 



With regard to the character on which Kiitzing relies as separating 

 his T. ventricosa from T.flocculosa, viz. the relative sizes of the central 

 and terminal inflations, I have only to say, that, in the numerous 

 specimens in my possession, I find these characters exceedingly 

 variable, and in no case have I met with valves in which the central 

 does not in some degree exceed the terminal enlargements. 



I therefore feel myself obliged to unite all these specimens under 

 one designation, and, although the specific name of ventricosa may 

 be the more appropriate one, must adhere to the term which has 

 priority and almost universal usage in its favour. 



1. Tabellaria flocculosa, Kiitz. Frustules indefinite; septa from 

 3 to 5 from each margin, slightly unequal. Length of frustule 

 •0006" to -0016". Valve with the central inflation the largest ; 

 stria? indistinct, about 36 in *001". v.v. 



Kiitz. Bacill. xvii. 21. Raben. Siissw. Diat. x. 2. Hass. Alg. xciv. 9. Ta- 

 bellaria ventricosa, Kiitz. Bacill. xxx. 74. Raben. Siissw. Diat. x. 5. 

 Conferva flocculosa, Dillw. Conf. xxviii. ? Bacillaria tabellaris, Ehr. 

 Inf. xv. 7. Diatoma flocculosum, Lyng. Tent. lxi. B. 4 ? Ralfs, Ann. 

 vol. 11. pi. ix. 3. ad specim. authen. in herb. Jenn. 



Fresh water : frequent in boggy pools. Wareham, Dorsetshire, Dec. 1849 ; 

 Plumpton, Sussex, May 1853 ; Grassmere, Westmoreland, and Rackham, 

 Sussex, Aug. 1853 ; River Lee, near Cork, April 1855, W. Sm. Jackswood, 

 and Coldbath Springs, Tunbridge Wells, Dec. 1842, Mr. Jenner. Lancashire, 

 March 1852, Mr. Johnson. Aberdeenshire, Dr. Dickie. Ben M c Dhui, elev. 

 3840 feet, Mr. P. Grant. Woodhead, Cheshire, May 1853, Mr. T. Brittain. 

 Isle of Arran, July 1853, Dr. Arnott. Ben Lawers, Aug. 1853, Professor 

 Williamson. Braemar, Aug. 1854, Dr. Balfour. Lough Mourne, Peterhead, 

 and Lough Island Reavey Deposits. (Falaise, M. De Brebisson. Lac Guery, 

 Mont Dore, elev. 4062 feet, June 1854, W. Sm.) 



Plate XLIII. 316. 



