<;S IJIUTISH DESMIDIACE^E. 



Length 4(i <tf'5[jL : breadth 40-55 (JL ; breadth of 

 i>t Inniis |-J '2\ [i. 



Kx< ; LA \ i >.- -Cumberland ! Westmoreland ! W. and 

 N.Yorks! Kssex! Warwicks! (TF*). Surrey! Sussex 

 (AW/*). .Hunts! Devon! (Harris). Cornwall! (Mar- 

 quand). 



\\ A L i > -Fairly general ! 



SCOTLAND. Sutherland, Ross, Inverness. Aberdeen 

 (at :j;>uO feet on Lochnagar !), Kincardine, Forfar, 

 IVrth! Argyle, Arran (Roy & Biss.). Dumbarton 

 (C(ti'U'i'). Kircudbright ! Orkneys ! Shetlands ! 



I RELAND.- -Donegal ! Clare Island and Inishturk Isle, 

 Mavo ! (Jalwav ! Kerry ! Down ! 



* / * 



Geogr. J Distribution- -France. Germany. Switzerland. 

 (Jalicia and Austria. Hungary. Italy. Norway. Sweden. 

 |)riiniark. Bornholm. Finland. Faeroes. Australia 

 (var.). I'nited States and Alaska. 



N/. murieatum is very widely distributed in the British Isles. 

 It is closely allied to St.hirsutum, from which it is distinguished 

 liy its usually larger size and much shorter spines, which 

 ;uv, a< a rule, reduced to small conical granules. Intermediate 

 forms between the two species are, however, not unknown. 



DO. Staurastrum pyramidatum West. 

 (PL CXXXVI1I, figs. 10-12; PL CXXXIX, fig. 16.) 



Shiiii-iixtrinn in in-ir, iinn, lorma West, Alg. X. Yorks. 1889, p. 293. 



nuricatum var. acutum West, Alg. X. Wales, 1890, p. 294, t. 5, f. 14;. 

 Him. Desm. Filmland, 1903, p. 22. 



,N7. iujrnin'iihiliini West. AI-. W. Ireland, 1892, p. 179; Alg. Engl. Lake Distr. 

 I2,p.20; Alg. aq. dulc. Lusitan. lS92,p. 1.103; West & G. S. West, Alg. 

 . England, IS'.7. p. 4tt4 ; Outwin. Karlsbad Algen, 1899, p. 6 ; West & 

 West, Alga-fl. tforks. 1902, p. 103 ; Alg. N. Ireland, 1902, p. 51. 



<VHs of medium size, 1^-U times longer than broad, 

 < I reply constricted, sinus usually almost linear, rarely 

 >ll .- lltl > "I"' 11 : semicells broadly pyramidate, apex 

 Bubtruncate, sides slightly convex, basal angles obtusely 

 rounded; cell-wall covered with stout acute conical 

 spines, arranged in concentric series round the angles, 

 "ining more scattered and sometimes emarginate on 



