80 MESSES. W. WEST AND G. S. WEST ON 



Tlie numerous specimens of Stcmrastrum aculeatmn, Menegh., examined from 

 N, America and Britain agree so ^ell with the figure given by Italfs (Brit. Desm. tab. 

 xxiii. fig. 2) that it is probable that the above variety of Nordstedt is another species. 



153. Staurastrum tohopekaligense, Wolle, Ereshw. Alg. of U.S. of Amer. p. 45, 



pi. 59. figs. 4, 5. . . 



Yar. TRiFURCATUM, nov. var. (Pi. IX. fig. 8.) Var. processibus paullo brevioribus, 

 apicibus trifurcatis, dentibus validis divergentibus ; processibus tribus ad angulos a 

 fronte visis minus patentibus. 

 Long, sine proc. 39 ^, cum proc. circ. 70 /i ; lat. sine proc. circ. 30 fx, cum proc. 70 /t; 

 lat. isthm. 13 jit. 

 No. 3. 



S. nonanum, W. B. Turn. (Ereshw. Alg. of E. India, p. 119, t. xv. figs. 14-15), seems 

 to be a form of this species with more globose semicells, which cause the three processes 

 at the angles to be more distant from the base of the semicells. 



Yar. QUADBANGrLARE, uov. var. (PL IX. fig. 9.) Yar. processibus apicibus trifurcatis, 

 dentibus minoribus; semiccUulse a vertice visae quadrangularcs, lateribus rectis 

 subconcavisve. 

 Lat. cum proc. 52-67 ^. 

 No. 3. 



This differs from the previous variety in its quadrangular vertical view and in the 

 processes being more slender and not having the large trifurcate apices. S. nonanum, 

 W. B. Turn., forma quadi^angulare, W. B. Turn. [l. c), is similar to this, but has shorter 

 processes bifurcate at the apices, and the sides of the vertical view are convex. 



154. Staurastrum tetraceri'M, Ealfs, Brit. Desm. p. 137, tab. xxiii. fig. 7. 



Long, cum proc. 18-23 ju ; lat. cum proc. 18-19 /t ; lat. isthm. 2-5-3-5 yu ; crass. 5 /u. 

 Nos. 1 and 3. 



Yar. UNDTJLATUM, nov. var. (PI. IX. fig. 6.) Yar. processibus distincte undulatis et 

 apicibus processuum emarginatis. 

 Long, sine proc. 11 ^u, cum proc. 27 n ; lat. cum proc. 27 /n ; lat. isthm. 5 ^u ; crass. 6iu. 

 No. 3. 



Class CCENOBIE^, 

 Order PEBIASTBE^. 



Genus PEDiASTRrM, Meyen. 



155. Pediastrtjm coxstrictum, Hass. Brit. Ereshw. Alg. p. 391, t. 86. figs. 15, 16 ; 

 Rabenh. El. Europ. Alg. iii. p. 77 ; Cooke, Brit. Ereshw. Alg. p. 42, pi. 17. fig. 2. 



Diam. coenob. 48-54 /u ; diam. cell, periph. 9-5-125 n. 

 Nos. and 3. 



