STAURASTRUM. 175 



Cooke (' Brit. Desm.' 1887, p. 147, t. 53, f . 6) figures a Desmid 

 which he attributes to St. furcatum var. candianum (Delp.) 

 Cooke (see PL CLV, fig. 5). Cooke's figure, however, shows 

 granulations round the lateral angles, which would indicate 

 greater affinity with St. subavicula West than with St. furcatum. 

 There is no indication of granulation in St. candianum Delp. 

 (' Desm. subalp.' 1877, p. 140, 1. 11, f. 22-24 ; see PL CLV, fig. 6). 

 Harris ('Desm. Dartmoor,' 1917, p. 29) has also recorded St. 

 furcatum var. candianum (Delp.) Cooke. It is probable that this, 

 too, would have been better referred to St. subavicula West. 



Var. subsenarium W. & G. S. West. (PL CLV, fig. 7.) 



St. furcation var. subsenarium West & G. S. West, >iew Brit. Fresrnv. Alg. 

 1894, p. 10, f. 53 ; Alg. S. England, 1897, p. 493 : Gronblad, Desm. 

 Keuru, 1920, p. 65, t. 3, f. 52, 53. 



This variety has a simple spine beneath each dorsal 

 process. 



Length, without processes, 20-29 \L ; breadth, includ- 

 ing processes, 25-39 [/. ; without processes, 18-32'ou; 

 breadth of isthmus 8-9'5ti. 



ENGLAND. - - Scandale, Westmoreland ! Dartmoor, 

 Devon ! 



WALES.- -Llyn Idwal (N. C.). 



IRELAND.- -Leenane to Westport, Mayo ! 



Geoar. Distribution.- -Finland. 



ij 



This variety differs from the typical form in the possession 

 of concentric series of granules round the angles of the semicell 

 as well as in the additional spines. 



161. Staurastrum senarium (Ehr.) Ralfs. 

 (PL CLVI, fig. 3.) 



Desmidium senarium Ehr. Micr. Leb. S. & N. Amer. 1843, p. 412, t. 4, f. 22. 

 Staurastrum senarium Ralfs, Brit. Desm. 1848, p. 216 ; Arch, in Pritch. 



Inf. 1861, p. 742, t. 2, f. 7 ; Rabenh. Flor. Europ. Alg. 1868, p. 220; 



Lund. Desm. Suec. 1871, p. 66 ; Nordst. Desm. Spetsb. 1872, p. 41 ; 



Wolle, Desm. U. S. 1884, p. 147, t. 52, f. 1 ; De Toni, Syll. Alg. 1889, 



p. 1155 ; Turn. Alg. E. India, 1893, p. 119, t. 15, f. 13 ; G. 8. West, Alg. 



Yan Yean, 1909, p. 68, t. 6, f. 13 ; Alg. Colombia, 1912, p. 1045. 

 Stephanoxanthium senarium Kiitz. Spec. Alg. 1849, p. 184. 

 Staurastrum furcatum var. senarium Joshua, Desm. Burma, 1886, p. 643. 



Cells small, about If times broader than long, deeply 

 constricted, sinus acute and open ; semicells elliptical 



