K()N(",L. SV. VKT. AKADKMIKNS II ANDLINOAK. BAM). 27. N:<) 3. fi7 



Thus, it. ap])ears that the forms of the l;evistriata' ai'e iiitei'inediate between the I'iiiniiliiriie and 

 the true Navicuhi'. 



The species of tliis gi'oiip ai-e usually inhahitaiits of hi'aekish water and a'stuaries, hut 

 there are also purely marine forms among them. 



Artificial key. 

 — straight 2. 



J ) Valve sigmoid X Rncrnin C'astr. 



_ j Axial area abruptly dilated into an orljiciilar tentral area or transverse fascia ... 3. 



\ Axial and central area uniting into a lanceolate or linear space 7. 



( Median strise of equal lengtli 4. 



' \ — — alternately longer and shorter X. lauta Grl'n. 



, ( Central area orbicular f) 



4. 



{ 



— a transverse fascia 6. 



) Valve acute or rostrate N. elcgans W. Sm. 



^ ' \ — obtuse N. Chyzerel Pant , N. disfcrvenda Pant., N. (/rata Pant. 



,. I Valve large. L. about 0,ofi mm X bitnminosa Pant. 



b. 



«. I ""^^ 



small. L. about 0,02 mm y. megastauros Ch. 



I Valve triundulate .... N. Areschougiana Grun. (N. prilpehralis r. Botteriana Gbun.). 



1 — not — 8. 



I Stria» radiate throughout i). 



8. 



\ Terminal strife convergent or parallel 12 



f J Median striae of equal length 10. 



-\ 



— alternately longer and shorter 11. 



J J Area very broad N. marginulata Cl. 



1 — medium sized N. palpehralis Breb. 



_. . I Area narrow N. VaJdiana Grun. 



\ — rhombic-lanceolate N. solida Cl. 



j Valve elliptical N. Kochii Pant. 



I — lanceolate 13. 



.,., ) 8tri» coarse, distant, 4 to 8 in 0,oi mm N. yarrensis Grun. 



' \ — closer, 8 to It in 0,oi mm X. halionata Pant. 



1. N. bitnminosa Pant. (1889). — V. liuear-laneeolate, with subacuminate ends. L. 0,o6.5; 

 B. 0,(114.') mm. Central pores of the median line somewhat ajiproximate. Axial area narrow, linear. 

 Central area a broad suborbicular fascia, almost reaching the margin. Striae 10 in 0,oi mm., 

 divergent in the middle, convergent at the ends. — Pant. II p. 42 PI. A^II f. 137. 



Brackish water: Hungary fossil! 



Var. latecaintata Pant. (1889). — V. linear, with broad, rostrate ends. L. 0,(i(i4; B. 0,01:35 

 mm. Striae 8,5 to 9 in 0,oi mm. — Pant. II 1. c. f. loo. 



Brackish water: Gyongyos Pata, Hungary fossil (Pant.). 



Var. rohusta Pant. (1889). — V. with capitate-rostrate ends. L. 0,08."); B. 0,018 mm. Cen- 

 tral area lanceolate. Strite 10 to 11 in 0,oi mm. — Pant. II PI. XI f. 202. 



Brackish water: Erdobenye, Hungary, fossil (Pant.). 



Var. signata Pant. (1889). — V. linear-lanceolate, with obtuse ends. L. 0,oh8; B. 0,018 mm. 

 Central area a transverse fascia reaching nearly to the margin. Stria* 11 to I2,n in 0,oi mm. — 

 Pant. II p. 43. X hit. r. valida PI. V f. 89. 



Brackish water: (Tyongyos Pata, Hungary, fossil (Pant.). 



Var. stnurophora Pant. (1889) — V. lanceolate. L. 0,0.54 to 0,075; B. O,oi.i to 0,oi5 mm. 

 Central area a broad fascia, reaching to the margin. Stria:". 10 to 11 in 0,oi mm. — Pant. II 

 PI. V f. 87, 88. 



Brackish water: Hungary fossil (Pant.). 



Var.y rhicta Pant. (1889). — V. lanceolate, with obtuse ends. L. 0,075; B. 0,oi6 mm. 

 Area lanceolate, very wide. Striae 12,5 in 0,oi mm. — Nav. cincta Pant. II p. 44 PI. XI f. 196. 



Brackish water: Hungary, fossil (Pant.). 



