KONGL. SV. VET. AKADEMIRNS HANDLINOAR. BAND 27. N:() 3. 79 



the margin being often very slight, in which case it is impossible to distinguisli it from certain 

 forms of P. (Hvenfens and F. stauroptera. 



17. P. platycepliala Eiib. (1854). — V. linear, 5 to (! times longer than broad, with broad, 

 subcapitate ends and sliglitly nndulate margins. L. O,o8;5 to 0,10.^); B. (),(»i7 to 0,0 1 8 mm. Median 

 line filiform with terminal fissnres in contrary directions. Axial area distinct, about '/., of the 

 breadth of the valve. Central area a more or less perfect fascia. Striai divergent in the middle, 

 convergent at the ends, 12 in 0,01 mm. — SfanropU'ra jddfyccphda Eiib. M. G. XV if: ri f. 9. 

 Piunnl. platyc. Cl. Diat. of Finl. p. 20 PI. II f. 1. 



Fresh water: Sweden: Rosslangen (Calmar Ian)! Pjesorn Dept. (Skelleftea)! ()jasjo Dept. 

 (Blekinge)! Finl. Suomenniemi Dept. (Viborgs liin)! Unrais socken (Vasa)! Pndasjarvi T)e])t. (Oster- 

 botten)! Scotland (Grove), France: Lac (jerardmer (Vosges)! 



P. platycephala is an isolated species, which shews no close relation to any known form. It 

 seems to come nearer to P. dirergens and P. legumen than to any other. 



18. P. divergens W. Sm. (1853). — V. lanceolate, gradually attenuated to the obtuse or 

 slightly capitate ends. L. 0,o7 to 0,14; B. 0,oi.') to 0,o2 mm. Median line filiform, with cvirved 

 terminal fissures. Axial area narrow, distinct, widened in the middle to a transverse fascia. Striae 

 11 to 12 in 0,01 mm., strongly divergent in the middle, convergent at the ends. — Br. I), p. 57 

 PI. XVI II f. 177. Nar. dir. A. S. Atl. XLIV f. 9. Wolle D. of N. A. XIX f. 21. 



Fresh water: Sweden (Lappland to Blekinge)! Norway (Stavanger)! Scotland (Premney 

 Peat, W. Sm., Dolgelly earth W. Sm., Loch Kinnord!) Finland! Bengal! New Zealand! Sandwich 

 Islands! N. America (Waterford, Maine)! S. America (Demerara River, Santos)! 



Var. runeata Grun. (1876). — V. with cuneate, subacute ends. L. 0,075 to 0,i; B. 0,oi4 to 

 0,02 mm. Central area a narrow fascia. Striae 11 in 0,oi mm. — A. S. Atl. XLIV f. 10, 11. 



Fresh water: Demerara River! 



Var. suhlinearis Cl. — V. elleptic-linear, gradually tapering from the middle to the obtuse 

 ends. L. 0,08 to 0,io; B. 0,oi4 to O.oi.'? mm. Striae 12 in 0,oi mm. — A. S. Atl. XLIV f. 20, 

 23. Nav. proccra Pant. II p. 52 PI. I f . 8 (1889)? 



Fresh water: New Zealand! America (Bemis Lake, White Mountains, Waterford, Maine; 

 Rio Burns, Brazil)! 



Var. elliptica Grun. (1884). — V. broad, linear to elliptical, with rounded ends. L. 0,o7 5 

 to 0,15; B. 0,01.') to 0,027 mm. Strite 8 to 11 in 0,oi mm. — Nav. div. var. ellipt. Grun. Fr. Jos. 

 Land D. p. 98 PI. I f. 19. Nav. div. A. S. Atl. XLIV f. 6 — 7. Nav. cardinalis var. africana Brun 

 D. espfeces nov. p. 33 PI. XVI f. 9. Nav. viridis var. staurophora Pant. Ill PI. VI f. 96 (1893)? 



Fresh water: Franz Jos. Land (Grun.), Norway (Tana Elf, Stavanger)! Sweden (Rosslangen 

 in Kalmar Ian, Ojasjo in Blekinge)! Finland! Scotland (Lsland of Lewis)! Australia (Blue Moun- 

 tains)! Greenland! Monmouth (Atl.), Demerara River! S. W. Africa, Ombika (Brun Coll.)! 



Forma ornata Grun. — Central area with a semicircular row of dots on both sides of the 

 central nodule. L. 0,12; B. 0,oi7 mm. Striae 10 in 0,oi mm. — Bengal! 



Var. Sehveinftirtii A. S. (1876). — L. 0, 11 to 0,12; B. 0,o2 mm. Axial area more narrow. 

 Median line oblique. Striae 11 in 0,oi mm. — Nav. Schweinfurtii A. S. Atl. XLIV f. 4, 5. 



Fresh water: Scriba Gattas (Atl.). 



19. P. Cardinaliculus Cl. N. Sp. — V. linear, with parallel margins and rounded ends. 

 L. 0,08 to 0,1; B. 0,0 15 to 0,0 18 mm. Median line filiform, with approximate central pores and 

 short, bayonet-shaped terminal fissures. Axial area less than V3 ^^ broad as the breadth of the 

 valve in the middle widened to a transverse fascia. Striae 9 in 0,oi mm., almost parallel or 

 slightly divergent in the middle and convergent at the ends. — PI. I f. 12. 



Fresh water: Scotland (Grove Coll.)! America (Canada, Crane Pond, French Pond, Houghton 

 Mich., Mexico)! 



