ti<i BRITISH DESMIDIACE^E. 



stniirn*innn ailesiocum Hil.se in Rab. Alg. Eur. no. 1826. 

 St. muricolum Nordst. Desm. Bornh. 1888, p. 203, t. 0, f. 19-22. 

 ,v/. ,,;/..*///// 1. minor \\'ittr. & Nordst. Alg. exsic. iios. 1474 & 409 (f. minor 

 Bee, I'r. .1. Liitkrmiillrr). 



CVlIs .small, up to 1| times longer than broad, deeply 

 , . ns1 nVtcd. sinus narrow, nearly linear for some distance, 

 tl ifii opening more widely; semicells subpyramidate- 

 trimcate, subreniform or even subsemicircular, usually 

 \\ idest near the base, angles broadly rounded ; cell- wall 



< ovcml with delicate hair-like spines arranged in con- 



J_ C-J 



< -en trie series round the angles. Vertical view triangular, 

 sides nearly straight, rarely very slightly convex or 

 C( >ncave, angles obtusely rounded, centre of apex smooth. 

 ( liloroplast axile, with a central pyrenoid in each semi- 

 cell. 



Xygospore roughly spherical, but somewhat angular, 

 I rovided with numerous stout processes repeatedly 

 forked at the apex. 



Length, without spines, 34-44 ;JL ; breadth, without 

 -pines, 31-35 \L ; breadth of isthmus 10-13 [j. ; length 

 of spines 1*5-2 pi; diam. zygosp., without processes, 

 38|JL ; with processes, 69 JJL. 



KXCLAND. Cumberland ! Westmoreland ! Lanca- 

 shire ! (Ralfs). W. and N. Yorks ! Leicester (Roy). 

 Kssex! Warwicks (Witts). Worcester! Surrey! Sussex 

 i/.V/.v). Kent! Hants! (Bennett). Devon! (Harris). 

 ( 'ornwall ! 



WALES. General ! 



SCOTLAND. General ! (Roy. & Biss.). Orkneys ! Shet- 

 lands! Rare in the plankton ! 



I RELAND. Donegal ! Mayo ! Galway ! Kerry ! Shores 

 of Loiio]] Ncagh ! Dublin and Wicklow (Arch.). Down ! 



Geogr. Distribution. France. Germany. Switzerland. 



Galicia and Austria. Hungary. Eoumania. Italy. 



Norway. Finmark. Sweden. Denmark. 



Bomholm. Faeroes. Spitzbergen. Greenland. United 



tat.-. Colombia. Brazil. Paraguay. 



St. hirsutum is distinguished from all allied species by the form 

 which are always wider at the base than else- 



