22 BRITISH DIATOMACE^E. 



their rearrangement should not have been made with more regard to 

 the original nomenclature, and the signification of the terms em- 

 ployed kept more strictly in view. 



1. Fragilaria capucina, Desm. Valves linear, cuneate at the sub- 

 acute extremities ; striae 40 in *00l". Length of frustule '001 2" 

 to -0025". v.v. 



"Var. /3. Valves attenuate towards the obtuse extremities, v.v. 



Var. y. Frustules subsiliceous, adhering imperfectly. Length *0033" to 

 •0042". v.v. 



Kiitz. Bacill. xvi. 3. Raben. Siissw. Diat. i. 2. Fragilaria Rkabdosoma, Ehr. 

 Inf. xv. 12. Prit. Anim. iii. 1/3, 174. Ralfs, Ann. vol. 12. pi. ii. 4. 

 Hass. Alg. xcv. 6. ad specim. authen. in Herb. Jenn. 



Fresh water: frequent. Lewes, Nov. 1851, Aug. 1852 and Aug. 1853. 

 River Lee near Cork, April 1855, &c., W. Sm. Glen Dee, Aberdeenshire, 

 Dr. Dickie. Quenmore, Lancashire, April 1852, Mr. Johnson. Lough 

 Mourne and Peterhead Deposits, &c. 



Var. /3. Well at Passage near Cork, August 1855, W. Sm. &c. 



Var. y. Rosthern Mere, Cheshire, September 1855, Dr. Arnott. 



This species is common at all seasons in still and running waters, but 

 seldom in much quantity or in an unmixed state. Its habit is stiff and un- 

 bending ; its colour under the microscope clear and translucent, and when dry 

 lustrous. Its filaments often resemble those of the last species, but usually 

 the front view of the frustule is narrower, and the valves linear and more 

 finely striated. Vars. a. and /3. are frequently intermixed. Var. y. has only 

 occurred to me in Dr. Arnott' s gathering, and is a very peculiar and probably 

 a sporangial condition. When dry the frustules in this variety shrink, except 

 in the central and extreme portions, and remain loosely attached by these 

 parts only. 



Plate XXXV. 296. 



2. Fragilaria virescens, Ralfs. V. linear or elliptical, suddenly 

 attenuated towards the produced extremities, which are obtuse; 

 striae 44 in -001". Length of frustule -0005" to -0027". v.v. 



ft. Frustules cohering by their angles only. 



Ralfs, Ann. vol. 12. pi. ii. 6. Kiitz. Bacill. xvi. 4. Raben. Siissw. Diat. 

 i. 1. Fragilaria pectinalis, Ehr. Inf. xvi. 1. Prit. Anim. iii. 1/6. 

 Fragilaria hyemalis, Ag. ad specim. authen. in Herb. Grev. Var. (3. Dia- 

 toma pectinale et Diatoma tenue, Kiitz. ad specim. authen. quse dedit 

 cl. De Brebisson. Diatoma virescens, Hass. Alg. xcv. 7. 8. 



Fresh water. Moanarone, County Cork, April 1855, W. Sm. Tunbridge 



