29 



23. L. membranacea Mer. 



Valve very narrow, gradually attenuateci tovvards the lower end 

 which is very narrow and rather acute, attenuated towards the up- 

 per end which is more or less rostrate. Pseudoraphe indefinite, stricie 

 very fine. Girdle face extremely delicate, narrow or very narrow, 

 cuneate, sometimes linear in its upper part, with almost acute 

 angles. Septa very shallow (0.0021- 0.002 2Ó mm.), very delicate, 

 slightly arcuate, septal puncta very small, Endochrome composed of 

 4-6 irregularly laciniated transverse bands. Individuals solitary or 

 forming small colonies of 2-4 (rarely more) frustules on very short 

 structurless stipes. Length o.o2i-o.o55 mm. (usually o.o33-o.043 mm.), 

 breadth of the frustule 0.0088-0.0012 mm., (usually 0.0057-0.0076 mm.) 

 breadth of the valve o.oo33-o.oo38 mm. 



Locality: Black sea, Crimea (lalta), common in certain places! 

 Mediterranean (Villefranche), rare! Adriatic (Pola), rare. 



The frustule is membranaceous and so delicate that with a so- 

 mcwhat low magnifying power it can scarcely be seen. This is the 

 most delicate species of Licmophorae. The endochrome has a very 

 peculiar appearance. 



24. L. Monksiae Mer. [fig. ló]. 



Valve broad in the middle, slightly attenuated towards the supe- 

 rior apex which is truncate, semetimes broadly rounded, more con- 

 siderably attenuated towards the lower end, which is narrow ; lower 

 part forming an elongated cone, with usually straight margins. Striae 

 fine, except at the lower end where they are distinct with an or- 

 dinary magnifying power, about i2-i3 in o.oi mm. Girdle face cup- 

 shaped with more or iess convex margins, upper angles rounded. 

 Septa very deep (o.oo6ó5 mm.), very fine, almost straight and parallel, 

 sometimes divergent above the septal puncta, the latter small, round, 

 very distinct, secondary punta large, adjoining the septa. Endochro- 

 me granular. F'orming small colonies on short structurless stipes or 

 solitary Length 0.01Ó2-0.041 mm. (usually 0.024-0 o33 mm.), breadth 



