Cosmmium] xi. DESMiDiACEyE (West). 351 



This is somewhat like C nitiduluni De Not. in form, but the very 

 thick and scrobiculate membraue easily distinguishes it. 



15. C. trifossum W. et G. S. West in Journ. Bot. 1897, p 116, 

 t. 367, f. 19. 



HuiLLA. — Inter Vtrimilariam, Morro de Lopollo ; April 1860. 

 No. 179. In paludibus exsiccandia ; April 1860. No. 176. Etiam in 

 graminosis paludo-<is juxta rivulum de Lopollo ; April 1860. No. 180. 



The three shallow notches seen in the front view of each setnioell 

 are due to the presence of three grooves running at right angles to 

 both the longitudinal and transverse axes. 



16. C. galeritum Nordst. in Vidensk. Medd. N.aturh. Foren. 

 Kjoben. 1869, No. 14-15, 209-210, t. iii. f. 26 (1870); W. et G. 

 S. West in Journ. Bot. 1897, p. 116. 



LiBON'GO. — Ad margines flum. Lifune ; Sept. 1858. No. 204. 



17. C. nitidulum Not. Desm. Ital. 42, t. iii. f. 26 (1867). 



C. rectosporum W. B. Turn, in K. Sv. Vet.-Akad. Handl. Bd. 

 25, no. 5, 69, t. X. f. 16 (1893). 

 Var. minor W. et G. S. West, I.e. 

 Htjilla. — In paludibus exsiccandis ; April 1860. No. 176. 



18. C. seenedesmus Delp. in Memor. Accad. Sci. Torino, ser. 2, 

 XXX. 5-6, t. vii. f. 28-34 (1878). 



Var. dorsitruneatum Nordst. in K. Sv. Vet.-Akad. Handl. Bd. 

 xxii. no. 8, 59, t. iii. f. 15 (1888) ; W. et G. S. West, l.o. 

 A small form with a perfectly smooth membrane. 

 HuiLLA. — In paludibus exsiccandia ; April 1860. No. 176. 

 LiBONGO. — Ad margines flum. Lifune ; Sept. 1858. No. 204. 



19. C. eethiopicum W. et G. S. West in Journ. Bot. 1897, 

 p. 116, t. 367, f. 20. 



PuNGO Andongo. — Inter Scytonema Myochroun v. chnrographicum et 

 Dichotriche.m gypsophilam ad latera boreal, et oocid. de Pedra Songue ; 

 April 1857. No. 12. 



Hdii.,la. — Inter Porphyrosiphonem, Notarisi prope lacum Ivantala ; 

 March 1860. No. 17. 



In outline this species calls to mind C. rectangulare Grun. 1868 

 i= C. Gotlandicum Wittr. 1872), but the more angular semi-cells, the 

 much broader isthmus, and the plications present on the upper half of 

 the semi-cells, at once distinguish it. 



20. C. pseudoprotuberans Kirchn. in Oohn, Kryptog. -flora von 

 Schlesien, Zweit. Bd. 150 (1878) ; Nordst. in Of v. K. Vet.-Akad. 

 Porh. no. 3, 8, t. vii. f. 3 (1885) ; W. et G. S. West, I.e., p. 117. 



A small form agreeing with var. pycimmum Gutw. (Flora 

 glonow okolic Lwowa, 54, t. ii. f. 9) in dimensions, but of the 

 same form as the type. 



HrriLLA. — In paludibus exsiccandis ; April 1 860. No. 176. 



21. C. polygonum Arch, in Pritch. Infos. 732 (1861). 

 EvMstrum polygonum Nag. Gatt. Einz. Alg. 120, t. 7a, f. 9 (1849). 

 Var. exile W. et G. S. West in Journ. Bot. 1897, p. Il7. 



