STAUKA STRUM. 185 



Cells with a slightly broader isthmus ; sides of 

 vertical view convex, straight, or slightly concave ; 

 granules minute but acute. 



o 



Zygospore similar to that of type, but with slightly 

 longer spines. 



Length 27-42 p. ; breadth 24-40 /x; breadth of 

 isthmus 9-18 p.. 



ENGLAND. Cumberland ! Westmoreland ! Lan- 

 cashire ! AV., X., and E. Yorks ! Surrey ! Devon ! 

 Cornwall ! 



WALKS.- -Fairly general in Carnarvonshire ! 



SCOTLAND. -- Sutherland ! Ross, Aberdeen, Kincar- 

 dine, Forfar, Perth ! (Roy $ m Bissett.) Renfrew ! Wig- 

 town ! Orkneys and Shetlands ! 



p 



IRELAND. - Donegal ! Mayo (and Clare Island) ! 

 Galway ! Kerry ! Down (up to 2000 ft.) ! 



Geogr. Distribution.- -France. Germany. Austria 

 and Gralicia. Portugal. Norway. Sweden. Bornholm. 

 Finland. Poland. N. Russia. Faeroes. Xova Zembla. 

 Spitsbergen. Greenland. Siberia. Sumatra. Mada- 

 gascar (var.). E. Africa. United States. Brazil. 

 Ecuador. 



There is only one reliable distinction between tins variety 

 and typical St. punctulatum, and that is in the nature of the 

 granulation. The granules of var. pii<.inui>um are sharp, 

 whereas those of the type are flattened or rounded. The 

 isthmus of the cells is also, as a rule, a trifle broader. There 

 is no difference in the shape of the semicells, except in vertical 

 view, in. which the sides are generally straight or slightly 

 convex. This difference is, however, of little importance, as 

 in many specimens the sides of the vertical view are concave 

 (consult PI. CXXVIII, fig\ lit}. Sometimes the cells are of 

 exactly the same outward form as those of typical St. punctu- 

 latum, but the granules are sharp (PI. CXXYIII, figs. 3 and 9). 

 Such forms belong* to the var. pygmssum only by reason of 

 their sharp granules. 



One form, which so far has onlv Leen observed from 



i/ 



Nacoogarrow Lough in Gaiway, has three series of slightly 

 larger granules forming a triangle on the apex of each 

 semicell ; length 48 fj. breadth 40/.<; breadth of isthmus 15 /UL 

 (PI. CXXYIII, fig. 4) . It should be known as forma TRILINEATA 



