P. T. Cleve: The Diatoms of Finland. 21 



and is surrounded by a distinct area, about Vs of the breadth of 

 the valve, and dilated on both sides of the central nodule. End- 

 fissures dissimilar and turned in opposite directions. Striae 12 in 

 O.oi m. m., divergent in the middle, convergent at the ends- 

 Lenght of valve 0,0 8 3 to 0,10 5 m. m. Breadth of valve 0,oit 

 m. m. to 0,oi8 m. m. 



This very distinct species is rather rare. I have seen it in 

 gatherings from the lake Rosslangen (Smaland, Sweden), from Lac 

 Gerardmer (Vosges), in the diatomaceous earths from Ojasjo (Ble- 

 kinge, Sweden) and Pjesorn (Skeleftea, Sweden). 



PL II, fig. I. 



Foss. Sa. 89, Tb. 90, Ob. 92. 



P. cardinalis Ehb. — V. H. Suppl. A. 5, A. S. XLIV, 1, 2. 



Foss. 97 (abundant). 



P. nobilis Ehb. — A. S. XLIII, 1. 



This species is easely distinguished by the large size of the 

 valves, which are dilated on the middle and at the ends, by the 

 coarse striae (4,5 in 0,oi m. m.), by the broad, longitudinal band 

 across the strise and the slightly complex raphe. The area oc- 

 cupies about one third of the breadth of the valve. 



Ab. 36. Sb. 8, 16. 



Foss. Ta. 94, 95, 96, 97, Tb. 90, Ob. 92, Lk. 104. 



P. gentilis Donk. — B. D. XII, 1. 



This species is distinguished from P. nobilis principally by 

 its smaller size and closer striae. It measures in length 0,14 5 to 

 0,2 m. m. and in breadth 0,0 2 2 to 0,0 3 6 m. m. The stria? are 

 akvays strongly radiant in the middle, 7 in O.oi m. m. The area 

 is somewhat less than one third of the breadth of the valve. The 

 raphe is distinctly complex. 



Sb. 16. 



Foss. Tb. 90, Ob. 92, Lk. 104. 



P. viridis Ehb. 



A great confusion exists about the forms, named by authors 

 P. viridis and P. major. Following A. Schmidt 1 admit as P. 

 viridis the fig. 20, 21, 11, 12, 13 on the Plate XLII in his Atlas. 

 P. viridis is distinguished by the following characteristic-. 



The valve is 5 to 6 times longer than broad, linear-elliptic, 

 with parallel margins, attenuated towards the rounded ends. The 



