1^6 RRITISH DESMIDIE^. 



20. C. setaceum (Ehr.) ; frond very slender, finely striated, narrow- 

 lanceolate, tapering at each extremity into a very long setaceous 

 beak, which alone is curved ; vesicles none or obscure. 



Closferium setaceum, Ehrenberg, Abhandl. der Berlin. Ak. 1833, p. 239 ; 

 Infiis. p. 97. t. 6. f. 11. Meneghini, Synop. Desmid. p. 235. Jenner, 

 Fl. of Tunbridge Wells, p. 1 96. Hassall, Brit. Freshwater Algce, p. 373. 



Closte?-ium rostratum, Bailey, Amer. Bacillaria in Amer. Joiirn. of Science 

 and Arts, v. 41. p. 303. t. 1. f. 36 (1841). 



Staui'oceras subulatum, Kiitziiig, Phycologia Germanica, p. 133 (1845). 



Stauroceras setaceum, Brebisson, in lit. (1846). 



Dolgelley, J. R. Waterdown Forest ; and near Cross-in-hand, Sussex, 

 3Ir. Jenner. Near Bristol, 3Ir. Broome. Near Aberdeen, Mr. P. Grant. 



Germany, Ehrenberg . Staten Island, New York, Bailey. Falaise, Bre- 

 bisson. 



Frond minute, many times longer than broad, very slender ; the body nar- 

 row-lanceolate, straight, attenuated at each end into a setaceous beak or awn, 

 which is longer than the inflated portion, curved downwards at the extremity 

 and blunt at the apex. The endochrome is pale, and does not extend beyond 

 the inflated part. Vesicles none or indistinct ; fillets none ; moving granules 

 not contained within a globule. 



The empty frond is colourless, and exhibits close and famt striae. 



Conjugated specimens are not uncommon. The process differs but little 

 from that described under the preceding species. The sporangium in this 

 species also appears like a continuation of the segments, and is quadrate or 

 cruciform. 



Closterium setaceum may be known from C. rostratum and C. gracile by 

 its slender beaks being longer than the body of the frond. 



Length of frond -^j-^ of an inch ; greatest breadth ^3^3^ ; distance between 

 the striae xyoT- 



Tab. XXX. fig. 4. a. frond with endochrome ; b. empty frond; c. sporangium. 



tt Frond minute, tapering, not rostrate ; empty frond colourless and 



without markings. 



21. C. CorwM (Ehr.); frond smooth, minute, curved, very slender; 

 extremities slightly attenuated ; ends obtuse ; vesicles none or 

 indistinct. 



/3. Frond more turgid. 



Closterium Cornu, Ehrenberg, Abhandl. der Berlin. Ak. p. 62 (1830) ; Infusor. 

 p. 94. t. 6. f. 5. Meneghini, Synop. Desmid. in Linncea 1840, p. 233. 

 Jenner, Fl. of Tunbridge Wells, p. 196. Kiitzing, Phycologia Germa- 

 nica, p. 131. Hassall, Brit. Freshwater Algce, p. 372. 



Closterium. tenue, Kiitzing, Synopsis Diatom. inLinncea 1833, p. 595. f. 78 ; 

 Phycologia Germanica, p. 130. 



Henfield, Piltdown Common, Battle, and Rackham Bogs, Sussex, Mr. Jenner. 

 Dolgelley, J. R. Ambleside, Mr. Sidebotham. 



Germany, Ehrenberg, Kiitzing. Falaise, Brebisson. 



