520 



STEPHANODISCUS. 



Sect. IV. Hyalino-radie/E. Valve furnished with radiating 



hyaline spaces. 



GENUS 183. STEPHANODISCUS (Ehr., 1845), Emend. Grun. 



a. 



Fig. 273, Stephanodiscits Niagara?, 

 a. Girdle view. b. Valve view. 



Valve circular, somewhat convex, with margin furnished with a 

 corona of spines, simple, acute, with fine puncta arranged in radiating 

 rows, interrupted by smooth spaces radiating, simulating lines ; centre 

 with scattered granules. 



In this genus have been arranged a rather numerous series of forms, most 

 of which probably do not belong to it. In the text will be found the type- 

 form of the genus S. Niagara" Ehr., found living at Niagara, and also at 

 Franz Josef Land. It has also been found in a fossil state at Buffalo and in 

 Prussia. 



S. Hantzschianus has been recorded in Belgium. 



S. Hantzschianus Grun. (Arct. Diat., p. 115; H.v.H. Atl., 



pi. 95, f. 10*; Type No. 482), plate 23, fig. 662. 



Valve small, with rather robust marginal spines, 6 to 9 in 1 c.d.m. ; stria? 

 radiant, formed of two parallel rows of very fine puncta, very difficult to be 

 seen. Diameter, 1 to 1*75 c.d.m. 



Fresh water. Brussels (Delogne). Antwerp (H.V. H.). 



It is probable that it will be met with in other countries in our zone. 



