152 



fine. Girdle face cuneate, moderatly broad, with rather rounded an- 

 gles; septa not profound (o 00225 mm.), septal puncta small, di- 

 slinct, round. Length 0.033-0.0427 mm., breadth of the frustule o.oogS- 

 0.0162 mm , breadth of the valve 0.00427-0.00Ó5 mm. 



Locality: Sea of Azof (Guenitschesk), rather common! Black sca 

 (Sebastopol), rare. 



It is dilfiCLilt, without entering in details and without figures, to 

 explain the differences existing between this variety and its type. It 

 is an intermediate form between L. debìlis and L. inflata. 



20. L. lata Mer. [fig. i3]. 



Valve broad, bottleshaped, upper part somewhat linear, or sligh- 

 lly attenuatcd to the summit, with parallel, sometimes convex mar- 

 gins, abruptly attenuated towards the lower thirdth or fourth, beco- 

 ming conica], lower apex narrow, rounded, upper broadly rounded 



Pseudoraphe rather broad, very distincl. 

 striae very fine. Girdle face moderatly 

 broad, cuneate, upper angles subrounded, 

 upper margin convex; septa very deep 

 (0.0114 mm.), arcuate, septal puncta di- 

 stinct, round. Endochrome granular. For- 

 ming numerous colonies on long stipes, 

 composed of two layers an external and 

 a thinner but denser inner one; mode of 

 ramification the same as in L. dalmatica, 

 L. gracilis, L. paradoxa (see diagram.). 

 Length 0.052-0.073 mm , breadth of the 

 frustule 0.0266-0.039 mm., breadth of the 

 valve 0.0 1 3-0.0 19 mm. 



Locality : California (San Fedro, very 

 common, Monterey, common). 



The structure ot the stipes is the same as in the whole groupe 

 to which this species belongs [L. dalmalica, L. gracilis, L. paradoxa, 

 L. commimis) ; the mode of ramification is a very peculiar and Con- 

 stant one. 



Diagrrara iHustrating tho low oi ra 

 mification of tho staìks in tho gioupo : 

 Paradnxac. 



