42 Acta Societatis pro Fauna et Flora fennica.. VIII, u. 2. 



Diploneis Ehb. 

 1. Didymcc. 



D. didyma Ehb. — V. H. IX, 5, 6. 



Foss. B. 101, 103. 



D. intermpta Kiitz. — V. H. IX, 7, 8. 



Mb. Ab. 100, Sinb. Ob. 83. 



Foss. B. 102, 103. 



2. Ellipticce. 



D. Smithii Breb. — V. H. IX, 12. 



Mb. Ab. 100, Sinf. Ob. 83. 



Foss. B. 101, 102, 103. 



D. elliptica Kiitz. 



A very great confusion prevails in the Nav. elliptica of dif- 

 ferent authors, so that is difficult to decide what form may be 

 regarded as the type. The fact is that several different species 

 are thrown together under the name Nav. elliptica. It is therefore 

 necessary to separate the different forms, and I have below made 

 an attempt in this direction so far as regards the forms of Fin- 

 land. As D. elliptica I regard the forms, which have a tolerably 

 large, more or less quadrate central nodule and arcuate furrows, 

 which closely follow the thickenings, which project from the cen- 

 tral nodule and enclose the raphe. The costse of D. elliptica are 

 strong, about 10 in 0,oi m. m., and alternate with rows of ge- 

 nerally distinct puncta, 10 to 12 in 0,oi m. m. The length of 

 the frustule is 0,0 2 7 to 0,0 3 7 m. m., the breadth 0,oi5 to 0,0 2 

 m. m. 



This form corresponds with the Nav. elliptica var. minor 

 Grun. (D. Ost. Ung. pag. 145), with the upper fig. 10 PL X in 

 Van Heurcks Synopsis and with the fig. 29, 32 in A. Schmidt At- 

 las. Nav. cocconeiformis Schum. (I pag. 188) belongs also pro- 

 bably to D. elliptica. 



Diploneis elliptica has been found on the following localities 

 in Finland: Lake Lojo (Ab. 45, 48), Suopohja (Kon. 41) and Pu- 

 dasjarvi (Foss. Ob. 92). 



