28 BRITISH DESMIDIACE^. 



Zygospore globose, ornamented with numerous 

 bluntly-rounded (or abruptly-sharp-pointed) spines. 



Length 70-91 p.; breadth 32-47 /*; breadth of isth- 

 mus 12-1 5 ft; thickness 26-29 /x; diam. zygosp. with- 

 out papilla 38'4-55'5ft; length of papillae 5-6*4 JJL. 



ENGLAND. Cumberland ! Westmoreland! (Ealfs). 

 W., N., and E. Yorks ! Lancashire ! (ttalfs). Cheshire 

 (Rolfs). Leicestershire (Roy). Warwickshire (Wills). 

 Gloucestershire (Rolfs). Surrey ! (Ealfs). Sussex 

 (Rolfs). Kent! Hants! (Rolfs). Devon! (Bennett). 

 Cornwall! (Ralfs). 



WALES. General and abundant (at 2,200ft. on 

 Glyder Fach, Carnarvonshire) ! 



IRELAND. General ! 



SCOTLAND. General and abundant ! (Roy fy Bissett). 

 Outer Hebrides ! Orkneys ! Shetlands ! Often in the 

 plankton ! 



Geogr. Distribution. France. Belgium. Germany. 

 Austria and Galicia. Hungary. Italy. Norway. 

 Sweden. Denmark. Bornholm. Finland. N. and 

 S. Russia. Faeroes. Iceland. Greenland. Central 

 China. Japan. India. Ceylon. Burmah (var.) 

 Siam. Singapore. Sumatra. Java. Australia (form). 

 New Zealand. Madagascar. E. Africa. Azores. 

 Sandwich Islands. United States. W. Indies (var). 

 Brazil. Paraguay. 



E. ansatum is one of the most generally distributed of the 

 British species of the genus. The " Euastrum ansatum } 

 described by Ehrenberg in 1832 is a Cosmarium which is now 

 known to occur in several parts of the world. The " Euastrum 

 ansatum" as known to all recent authors is the one originally 

 described by Ralfs in his ' British Desmids/ and therefore 

 Ralfs must be regarded as the authority for this species. 



The Desmid partly described and figured by Hassall under 

 the name of "Euastrum circulars" is most probably a form 

 of E. ansatum, as was pointed out by Lundell in 1871. 

 Hassan's description, however, is so poor and his figure so 

 had, that certain identification is impossible. 



The zygospores observed by Roy appear to have differed 

 somewhat from those we have ourselves observed. Roy 

 describes the zygospores as furnished with numerous " short, 



