176 RRITISH DESMlDIEiE. 



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. 



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

 Infus. p. 97. t. 6. f. 11. Menegliini, Synop. Desmid. p. 23.5. Jenner, 

 Fl. of Tunbridffe Wells, p. 1 96. Hassall, Brit. Freshwater Algce, p. 3/3. 



Closterium rostratum, Bailey, Arner. Bacillaria in Amer. Journ. of Science 

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



Stanroceras suhulatum, Kiitzing, Phycologia Germanica, p. 133 (1845). 



Staiiroceras setacenm, Brebisson, in lit. (1846). 



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

 3Ir. Jenner. Near Bristol, Mr. Broome. Near Aberdeen, 31r. 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 faint 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 y^ of an inch ; greatest breadth -^-^tr '■> distance between 

 the striae tittt- 



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



tt Frond mhiute, 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. 



ClosteriumCornu, Ehrenberg, Abhandl. der Berlin. Ah\ p. 62 (1830) ; Infusor. 

 p. 94. t. G. f. 5. Meneghini, Synup. Desmid. in Linncea 1840, p. 233. 

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

 nica, p. 131. Hassall, Brit. Freshwater Algce, p. 3/2. 



Closterium tenve, Kiitzing, Synopsis Diatom, in Linncea 1833, p. 595. f. 7S ; 

 Phycologia Germanica, p. 130. 



Henfield, Plltdown Common, Battle, and Rackham Bogs, Sussex, 3//'. Jenner. 

 Dolgelley, /. R. Ambleside, Mr. Sidcbotham. 



Germany, Ehrenberg, Kiitzing. Falaise, Brebisson. 



