59 

 (o.oi52 mm.), slìghtly arcuate, thìn below the septal puncta, thick 

 obove them. Length 0.093-0.179 mm , breadth of the valve o.oii- 

 0.017 mm. 



Locality: California (Monterey), common. 



L. Thumii has no dose relation to any other species. I need not 

 to explain in whose honour I bave named this species, every dia- 

 tomist knowing M.r E. Thum, of Leipzig. 



