360 XI. DESMiDiACE^ (West). [Siaurastrum 



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



This species has about twenty-five very short spines on each of 

 the three angles of a semi-cell, over which is placed a pair of slender, 

 erect and longer spines. It most nearly approaches S. Welwitscliii in 

 form and arrangement of spines, but differs from it in being triangular 

 in vertical view, and in having a pair of slender erect spines in place 

 of the single stout spine of the latter species. The angles are also 

 furnished with more numerous and shorter spines, and it is moreover 

 a smaller, much more constricted species. 



Var. pulchrum W. et G. S. West in Journ. Bot. 1897, p. 179, 

 t. 369, f. 3. 



HuiLLA.— In editis de Morro de Lopollo ; Feb. 1860. Xo. 192. 



12. S. actinotum W. et G. S. West in Journ. Bot. 1897, p. 180, 

 t. 369, f. 4. 



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

 This peculiar Staurastncm does not appear to be closely related 

 to any other. 



Var. simplex W. et G. S. West, I.e., t. 369, f. 5. 

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

 No. 179. 



13. S. cassidum W, et G. S. West in Journ. Bot. 1897, p. 180, 

 t. 368, f. 21. 



HuiLLA. — In uliginosis editioribus prope Humpata, Empalanca et 

 Lopollo ; May 1860. No. 15. 



This species is distinguished from S. trihedrcde Wolle (Desm. U.S. 

 123, pi. 40, f. 12-14 ; W. et G. S. West in Trans. Linn. Soc. 2nd ser. 

 v. 260-1, t. xvi. f. 29) by its smaller size, its more conical semi-cells 

 with comparatively broader apices and almost straight sides, by the 

 form of its vertical view, and by the much smaller and more numerous 

 markings on the membrane. S. trihedrale var. rhomboideum W. et 

 G. S. West {I.e. f. 30) seems to be intermediate in form between this 

 species and S. trihedrale, but it has the characteristic basal angles, the 

 narrow apex, and the markings of S. trihedrale, whereas none of these 

 characters are possessed by S. cas>iiduni. 



14. S. areolatum W. et G. S. West in Journ. Bot. 1897, p. 180, 

 t. 367, f. 17. 



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

 No. 179. 



This is very distinct from S. coamariokles Nordst. [in Vidensk. 

 Medd. f. d. naturh. Foren. (1869), no. 14-15, 223, t. iy. f. 43 (1870) ], 

 and it is different in the form of its front view and in its membraue 

 from any species of Co^iiumum. Borgesen, in Vidensk. Medd. f. d. 

 naturh. Foren., Kjoben. 1890, 50 (1891), figures (under a wrongly 

 stated magnification !) under the name of S. eoamarioida forms which 

 he suggests may be trigonal and tetragonal forms of several species 

 of Cosmarkun. His fig. 2 somewhat approaches this species in form, 

 but it has different basal angles and a very different sinus. 



15. S. scrobiculatum W. et G. S. West in Journ. Bot. 1897, 

 p. 181, t. 368, f. 18. 



HuiLLA. — In uliginosis editioribus prope Humpata, Empalanca et 

 Lopollo ; May 1860. No. 15. 



