part more or less linear, superior apex broad, truncate. Pseudoraphe 

 indefinite, striae very fine. Girdle face narrowly cuneate, with up- 

 per angles slighlly rounded, outlines very delicate. Septa shallow 

 (00014-0.00 19 mm.), gently arcuate, septal puncta very small. Endo- 

 chrome granular. Sessile or on short, slightly ramifica stalks, usually 

 parasitic on frustules oi L. graiidis. Length o.oiò-o.o285 mm., breadth 

 of the frustule o.ooóóS-o.oogS mm., breadth of the valve 0.0029- 

 o.oo33 mm. 



Locality : Mediterranean (Villefranche), rather common. 



Differs from small individuals of L. dehilis by the broad, trun- 

 cate superior apex of the valves which in L. debilis is always atte- 

 nuated and more or less acute; the frustules are also more delicate. 



29. L. permagna Mer. [fig. 20]. 



Valve of medium breadth, bacilliform, very slightly and gradually 

 attenuated from the summit to the lower end, with straight margins; 

 superior apex strongly attenuated, with summit acute, inferior apex 

 broad, rounded, not inflated. Pseudoraphe rather broad, very distinct, 

 striae not very delicate, about 18-19 in 0.0 1 mm., parallel throu- 

 ghout, crossed by straight longitudinal lines. Septa very shallow, 

 o.oo33-o.ooò65 mm. (average of 11 cases: 0,00453 mm.). Length 

 0.125-0.206 mm., breadth of the valve 0.0143-0.018 mm. 



Locality : New Guinea (german possessions), rather common. 



But for the acute superior apex and the longitudinal lines this 

 species could be considered as nearly allied to L. Jiirgensii. By 

 the longitudinal lines it reminds L. Jiirgeimi var. capensis Grun. 



3o. L. pontica Mer. [fig. 21]. 



Valve of medium breadth, cuneate, very slightly attenuated from 

 the summit to the base, with straight margins, lower end somewhat 

 broad, rounded, sometimes slightly produced, superior apex broadly 

 rounded. Striae very fine. Girdle face moderatly broad, cuneate, Avith 

 very thick margins, upper angles very rounded, lower apex some- 

 what broad, rounded; septa superficial, straight, septal puncta very 



