KONGL. SV. VET. AKAUEMIENS HANDLINGAK. BAND 27. N:0 3. 



195 



' 10. A. baccata Leud. Foetm. (1879). — Linear, with broad, rounded ends. L. 0,i; B. 0,02s 

 mm. Lower V. with wide and irregular axial area. Central area large and irregularly transverse. 

 StrisE 7 in 0,o i mm. formed of large puncta, arranged in undulating, longitudinal rows. — Stanro- 

 neis baccata Leud. D. de Ceylan p. 37 PL III. f. 35. Achnanthes curvata Leud. 1. c. PI. I f. 5? 

 A. bacc. Icon. n. PI. Ill f. 3. 



Marine: Colombo, Ceylon (Le Tourneur Coll.)! 



11. A. groenlandica Cl. (1873). — Linear with rounded ends. L. 0,o4 to 0,o6; B. 0,oo5 

 to 0,007 mm. Upper V. with narrow axial area and strong costate strite, 4,5 to 6 in 0,oi mm. 

 crossed by a longitudinal line. Lower V. with indistinct axial area. Central area a broad trans- 

 verse fascia. Central pores of the median line somewhat distant. Stride 5 to 6 in 0,oi mm. 

 slightly radiate, formed by 3 to 4 large, distant puncta. Frustule genuflexed. Connecting zone 

 with a row of puncta, 6 to 7 in 0,oi mm. Lower valve with rudimentary diaphragms. — Ach- 

 nantkidmm groenlandicum Ol. A. D. p. 25 PL IV f. 23. Achnanthes gr. Gkun. A. D. p. 20. 

 Cl. Vega p. 460 PL XXXV f. 3. 



Marine: Arctic America! Greenland! Spitsbergen! Finmark! Behrings Island! 



12. A. crenulata Grun. (1880). — Elliptical to elliptic-linear, obtuse, with crenulated 

 margin (2,5 to 3 undulations in 0,oi mm.). L. 0,034 to 0,076; B. 0,oi5 to 0,02 mm. Upper V. 

 with very excentric and narrow axial area. Strise parallel, 6 to 6,5 in 0,oi mm. coarsely punc- 

 tate; puncta 6 to 7 in 0,oi mm. Lower V. with narrow but distinct axial area. Central area a 

 transverse fascia. Striie 6 to 7 in 0,oi mm. slightly radiate throughout, punctate; puncta 6 to 7 

 in 0,01 mm. — A. D. p. 20. Cl. Diatomiste I p. 50 PL IX f. 3, 4. 



Fresh or brackish water: New Guinea! Samoa! Australia (Daintree River)! 



Aclinantlies Bory S:t Vincent (1822). 



Outline linear to elliptical or lanceolate. Upper valve with central and narrow axial area, 

 without central nodule and median line. Lower valve with median line and stauroid central 

 nodule. Axial area narrow. Structure similar in both 

 valves: transverse costse, alternating with double rows 

 of small puncta, arranged in decussating rows. Frus- 

 tule genuflexed, stipitate. No annulus. Connecting- 

 zone transversely striate. The cell-contents of A. lon- 

 gipes have a number of scattered, rounded or elongated 

 chromatophore-granules . 



Achnanthes, limited as above, has a great resem- 

 blance to Achnanthidium, as regards the manner of 

 living and the form of the frustule and the valves, but 

 the structure is different. Of the afiinities of Achnan- 

 thes little can be stated. The structure of A. javanica 

 and of A. bengalensis, which, according to Gkunow, have 

 longitudinal lines, has some resemblance to that of 



ScoUotropis and Gomphoneis. Mastogloia Grevillei has a similar structure, but differs greatly in 

 other respects. There is also some resemblance to Mastoneis, the central nodule of which also 

 forms a stauros, although short. 



1. A. longlpes C. Ag. (1832). — Linear-elliptical, with broad, rounded and frequently 

 cuneate ends, usually slightly constricted in the middle. L. 0,oo5 to 0,i8; B. 0,oi2 to 0,o27 mm. 

 Upper V. convex. Axial area a central, linear silicious rib. Costse 7 to 8 in 0,oi mm. parallel, 



LJ^j 



Achnanthes longipes with cell-contents: 500 times 

 magnified. 



