158 BRITISH DESMIDIACE^l. 



concave, or slightly convex, angles produced and sub- 

 mamillate. 



Length 1 1 0-1 6-5 /u, ; breadth (Vo-8'8ft; breadth of 

 apices 1*6-3 /A ; diameter of zygosp. 23-30 /x. 



EXULAXJ*. Cumberland! Westmoreland ! 

 W. and N. Yorks ! Cheshire (-/'"//) Leiceste 

 Essex! Warwick (IF///*). Middlesex! Surrey! Sussex 

 (/iW/s). Kent! Hants! (.So//). Devon (Bennett). 

 Cornwall ! (Marquand). 



WALES. Near Dolbadarn Castle ! , Llyn Cwlyd ! , 

 Capel Curig ! (( '<>< >!,(; fy TFv7/.s), and Pen-y-gwryd (R<>'/), 

 Carnarvonshire. Holyhead, Anglesey ! Dolgelly, 

 Merioneth (Ralfi). 



SCOTLAND. General ! (Roy Risse.tt). Shetlands ! 



IRELAND. Donegal ! Mayo ! Galway ! Kerry ! 

 Dublin and Wicklow (Archer). Antrim ! 



d'royr. Distribution. France. Germany. Austria 

 and Galicia. Hungary. Portugal. Norway. Sweden. 

 Denmark. N. and Central Russia. Poland. Faeroes 

 (form). Nova Zembla. Siam. Java. Samoa (var.). 

 Australia (var.). Central Africa. United States. 

 Brazil (var.). 



This species has considerable resemblance to Cl. grad/c 

 Breb., with some forms of which it may easily he confounded. 

 It is, however, more regularly curved than CL grarilc and the 

 apices are more truncate. The zygospore is very different 

 from that of Cl. gracile, and conjugated specimens could not 

 be confused. It should also he compared with CL tuniidiun. 



Balfs' statement that the cells are " five to eight times 

 longer than broad" is erroneous. 



35. Closterium abruptum West. 

 (PI. XX, figs. 6-10.) 



Closterhim Hln-it^him West, Alg. Eng. Lake Distr. 1892, p. 719, t. 9, f . 1 ; 

 Johns. Bare Desm. U.S. II, 1895, p. 291, t. 239, f. 5 ; West & G. S. 

 West, Some N. Amer. Desm. 189(5, p. 23(3, t. 13, f. 14, 15 ; Nordst. Index 

 Desm. ]S9(i, p. 36; West & G. S. West, Alo-. S. England, 1897, p. 479; 

 Alga-fl. Yorks. 1900, p. 54 ; Alg. N. Ireland, 1902, p. 22. 



Cells small, about 10 times longer than their 

 diameter, slightly curved, outer margin about 55 of 

 arc, median portion of cells almost straight, more 



