52 R. Gronblad, New Desmids. 



pi. 7 f. 10). This species is also in Finland very much 

 rarer than X. ant Hop. and X. cristatum. 



var. oronense West, Desm. N.-Amer. pi. 15 f. 25. 

 Forma semicellulis plus depressis, in centro circulo simplici 

 granulorum ornata. Cum spin. long. 72, lat. 72, isthm. 19 ,". 

 [N:o 902]. — The Finnish form is generally more depressed, 

 the central granules are regularly arranged in a ring. At 

 the basal angles 2—3 granules. Just below the basal spines 

 is sometimes a small accessory one. — The form described 

 and figured by Schmidle as „f. lapponica" (Pite Lappm. 

 1898 pi. 1 f. 15) is nothing but a form of this variety: var. 

 oronense f. lapponica (S c h m.) nob. 



Hab. Lempaala (W). — PI. 4 fig. 38. 



var. longispinum nova var. Cellulae multo maiores. 

 Semicellulae angulis basalibus valde rotundatis, lateribus 

 vix angulatis, sed valde convexis, apice recto latioreque, 

 ut quasi sexangulato-trapezo-subellipticae fiant; in utraque 

 semicellula aculei 6 geminati vel haud raro in angulis su- 

 perioribus aculei gemini inferiusque 3 vel 4 vel 5 plus 

 minus irregulariter defixi; aculei omnes graciliter curvati, 

 maxime autem apicales. Membrana subtiliter porosa, in 

 area centrali vix protuberanti glabra incrassata luteola. A 

 vertice visum crassius. Massa chlorophyllacea parietalis e 

 laminis 4 parietalibus pyrenoidibusque totidem composita. 

 Cum spin. long. 95 — 103, lat. 84—95, sine sp. long 66 — 70, 

 lat. 57—61, isthm. 19—23, long spinae 13—19 it. [N:o 989]. 



This remarkable variety is easily distinguished by its 

 larger size and its much longer, always slightly curved 

 spines. Basal angles more rounded, the form of the semicells 

 resembling X. antilopaeum. The semicells usually possess 

 six pairs of spines, but the spines are, howewer, frequently 

 more or less irregularly arranged and vary in number 

 from 10 — 14 in each semicell. The distance between the 

 apical spines is greater and the basal ones are placed more 

 upwards from the base of the semicells. Central area 

 conspicuously thickened and of a yellowish colour but 

 al w ay s quite smooth. This variety very much resembles 



