most parallel margìn, becoming more strongly attenuateci near the 

 lower end, which is conical, terminating in a point, upper end some- 

 what attenuated, with apex rounded. Pseudoraphe fine, striae very 

 variable, from 12 to 17 in 0.0 1 in the middle. Girdle face very 

 narrow, linear, becoming suddenly conical at the lower end, upper 

 angles slightly rounded; septa very shallow (0.0014 mm.), some- 

 times quite superfìcial, straight, thin, septal puncta very distinct, 

 elongated. Endochrome granular. Length 0.0605-0.048 mm. (average 

 of 25 cases 0.121 mm.), breadth of the girdle face 0.00Ó7-0.01 14 mm., 

 breadth of the valve 0.0038-0.0072 mm. 



Locality: Adriatic (Pola), common! Black sea (Sebastopol), very 

 rare. 



The girdle face of this very peculiar species reminds much more 

 a Synedra than a Licmophora. The variation in size is unusually 

 great. 



40. L. subundulata var. tenella Mer. 



Differs from the type species by its smaller size and more deli- 

 cate appearance, the constrictions of the valve are fainter, usually 

 indistinct, the girdle face broader, the septa almost always superfì- 

 cial, with very small marginai puncta, the striae fìner, 18-22 in 0.0 1 

 mm. Length 0. 0476-0. o655 mm.. breadth of the girdle face 0.0057- 

 0.0095 mm., breadth of the valve 0.0029-0.0033 mm, 



Locality: Adriatic (Pola), rather rare, mixed with the type. 



41. L. Thumii Mer. [fìg. 3o]. 



Valve of medium breadth, strongly davate, slightly arcuate and 

 asymmetrical, rarely symmetrical, upper part inflated, attenuated to- 

 wards the superior apex which is broad, truncate; abruptly attenua- 

 ted at the superior '/^ becoming narrow and almost linear, inferior 

 apex slightly inflated. Pseudoraphe broad, very distinct, terminating 

 at the summit of the valve in a pseudonodule, striae 16-17 ^^ O-oi 

 mm. at the lower end as well as in the middle. Girdle face cunea- 

 te, with upper angles subacute: frustule rather strong. Septa deep 



