TQO 



NAVICULA. 



N. compressicauda Ad. Schm, (Nordsee, p. 91, pi. 2, f. 35 ; 



Atl., pi. 46, f. 62*), plate 25, fig. 725. 



Valve broadly lanceolate elongated, with apices obtuse, compressed ; striae 

 robust, finely divided crosswise, distant, about 5 in 1 c.d.m, radiant at the 

 median portion of the valve, perpendicular at the apices, not reaching to the 

 raphe; those in the middle distant ; central nodule surrounded by a rounded 

 hyaline area. Length, 11 to 12 c.d.m. Breadth, 2^25 c.d.m. 



Marine. North Sea at Solsvijj (Ad. Schm.), 



2. Valve with somewhat eccentric structure. 



N. Cesatii Rab. (Sussw. Diat, p. 39, pi. 6, f. SgCy/nbel/a I 

 H.V.H. Atl., pi. 8 f., 35 * ; in Types No. 47, 484, etc.), plate 3, fig. 143. 



This diatom, which is perhaps a Cymbella, has very narrowly lanceolate 

 valves and terminal nodules, considerably distant from the apices of the valve. 



Fresh water. Berg. (Delogne), England. 



N. inaequilatera Lag. (Diat Spitzb., 1873, p. t,3, p 1 - 2, f. 10* 



Cymbella subaqualis W. Sin.), plate 25, fig. 727. 



Valve lanceolate, narrow, with somewhat unequal margins, apices rostrate- 

 capitate. Transverse striae radiate, rather fine, 12 to 14 in 1 c.d.m.. Length 

 of valve, 3 to 4 c.d.m. Breadth, about 75 to 1 c.d.m. Girdle face with straight 

 margins, not inflated at the median portion. 



Fresh water England (Balfour and W. Sm.). Spitzbergen (Lagerstedt). Will probably 

 be found elsewhere. 



III. Didymae. 



A . Valves having both beads and casta:. 



Valves fur- 

 nished with 

 robust costse -J 

 throughout 

 its extent. 



Intercostal 

 beads very 



small, 



difficult to 



be seen. 



f Median costas reaching up to the mar- 

 gin of the valve ; two rows of beads 

 between the costae . . . N. Crabro. 



Median costas not reaching up to the 

 margin of the valve ; a single row of 

 beads between the costas . . N. interrupta. 



Intercostal beads very coarse with smaller beads interposed N. Beyrichiana. 

 I Valves with costae more distant at the constriction . . N. splendida. 



