226 



NAVICULA. 



XXII. Minutissimae. 



I. Frustules not united into bands. 



f Valve with coarse striae simulating costee 



i I 



I -s 



-! - 

 8 

 *c 



(73 



Valves ( Valve somewhat inflated at the median portion 

 having 



( Valve linear-elliptic 



( Valve elliptic 



a Valve 



pseudo- not 



stauros. L inflated. 



f 



f Valve lanceolate, narrow, stria; radiate, very dis 



Valve 

 without 



a 

 pseudo- 

 stauros. 



tinct 



N. incerta, 

 N. Seminulum. 

 N. minima. 

 N. atomoides. 



. N. Falaisensis. 



1 Valve lanceolate, ( Marine : 24 30 since in 1 



rather bioad, c.d.m. . . . N. Bahusiensis. 



striae scarcely J 

 Valve radiant, the ; 



lanceolate. -| median more | Fresh water : 36 strire in 1 



apparent. L c.d.m. . . . N. minuscula. 



Valve rather broad, striae radiate, alternately long 

 and short at the median portion of the valve, 

 apices obtuse . . . . N. cocconeiformis. 



Valve very narrow, striae parallel, apices not sub- 

 L rostrate . . . . N. Bulnheimii. 



" Valve deeply constricted at the median portion . N. binodis. 



( Valve inflated at the median portion . N. perpusilla. 



f Valve linear elongate . N. lepidula. 



I Valve elliptic, sublanceo- 



Valve 



not 



lanceolate. 



Valve 

 not con- -; 

 stricted. 



I 



Valve 



not 

 inflated. 



late 



N. exilissima. 



I Valve elliptic, suborbicu- 



i_ late . . N. Atomus. 



II. Frustules united in bands. 



' Valve with median and terminal portions inflated ... N. contenta. 



,, , ( Valve linear-elliptic, with margin furnished with coarse, distant beads . N. Gallica. 

 Valve J ' 



not so. I vklve linear, inflated in the middle, without coarse beads at the margin N. Flotowii. 



/. Frustules not united in long bands. 



a. Valve furnished with costas. 



N. incerta Grun. ! (H.V.H. Atl., pi. 14, 43*). P late 5. fi S- 22 7- 



Valve linear lanceolate, with apices somewhat produced ; striae in form of 

 robust costae, reaching almost to the raphe, somewhat distant, about 15 in i 

 c.d.m. Length, 1*5 c.d.m. Breadth, -6 cd.m. 



Marine. Blankenberghe. 



