KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 26. N:0 2. 15 



Var. Pokornyana Grun. (1860). — Frustule slightly constricted. L. 0,065 to 0,o87; B. 0,o2 to 

 0,027 mm. Junction-line slightly sinuose. Valve narrow, linear, with rostrate ends, and almost 

 straight median line. — Grun. Verh. 1860 p. 569 PL VI f. 9. 



Brackish water: Nensiedlersee (Hungary); Sea of Kara (Grun.). 



The above description is from the work of Grunow. In CI. M. D. N:o 256 (Lymington, 

 England) occurs a form, determined by Grunow as A. Pokorn. L. 0,o9; B. 0,04 mm. Striae 

 16 in 0,01 mm., coarsely pu.nctate on the keel. Junction-line slightly sinuose. Keel strongly 

 sigmoid. 



Var. punctulata Grun. (1880). — Frustule slightly constricted. L. 0,o37 to 0,095 mm. B. 0,o2 

 to 0,023 mm. Junction-line not sinuose, with a row of small puncta. Striae about 27, on the keel 

 24 in 0,01 mm. — A. pal. v. punct. Grun. A. D. p. 62, PI. IV f. 84. Franz Josephs L. D. p. 53 

 (105), PL I f. 54, 55. 



Brackish water: Sea of Kara! Franz Josephs Land (Grun.), Cape Wankarema! 



Var. Nereis Lewis (1861). — Frustule strongly constricted in the middle. L. 0,05 to 0,i i4 mm 

 Junction-line not sinuose, but with distant puncta. Striae 22 in 0,oi mm. V. narrow, lanceolate, 

 with sigmoid median line. — A. Nereis Lewis. Proc. Acad. N. Sc. Philadelphia 1861 p. 64. — 

 A. plicata var. japonica Castr. Challenger Exp. D. p. 40, PL XXX, f. 8. 



Marine: Atlantic coasts of N. America (Lewis). 



Var. dilatata Pant. (1891). — Frustule strongly constricted. L. 0,i39. Height of the valve 

 0,02.5; at the constriction 0,oi05 mm. Junction-line crenulated. Strife 25 in O.oi mm. — A. dila- 

 tata Pant. II. p. 55, PL X f. 179. 



Brackish water: Hungary, fossil (Pant.). 



This form only differs from var. Nereis by its somewhat larger size. 



Var. ioreaJis Grun. (1880). — Frustule slightly constricted. L. 0,o7 9 to 0,085; B. 0,0 2 8 to 

 0,03 mm. Junction-line slightly arcuate, not sinuose. Striee on the keel 23, on the valve and the 

 connecting zone 26 in 0,oi mm. — A. pal. var.? borealis Grun. A. D. p. 62, PL IV f. 85. 



Brackish water: Sea of Kara (Grun.), Cape Wankarema! 



Var. duplex Donk. (1858). — Frustule in L. 0,02 to 0,o66; B. 0,oi to 0,04 mm. Junction-line 

 arcuate, not sinuose. StriiE very fine. V. narrow, lanceolate, with strongly sigmoid median line. 

 — A. dupl. DoNK. T. M. S. VI p. 29, PL III f. 13. — A. pal. v. ^upl. V. H. Syn. p. 121, PL 

 XXII f. 15, 16. 



Brackish water: Greenland! North Sea (Sweden! England, Donk., Belgium V. H.) Hungary, 

 fossil (Pant.). 



Var. hyalina Eulenst. (1880). — As Var. duplex but smaller. L. 0,017; B. 0,o35 mm. — 

 A. hyalina Eut. in V. H. Syn. PL XXII f. 17. 



Brackish water: Cette (Grun.). 



A. paludosa is a very variable species, closely connected with A. alata. Nearly akin to 

 A. paludosa, perhaps a variety, is A. Kiltzingiana Grev. (1863 Edinb. N. Ph. J. XVIII p. .184 

 f. 6) from Queensland. The frustule is deeply constricted. L. 0,i28 mm. The junction-line is 

 not sinuose. 



2. A. Dusenii Cl. N. Sp. — Frustule membranaceous, strongly constricted in the middle, 

 the segments being almost orbicular. L. 0,13; B. 0,ii at the constr. 0,o7 mm. Zone with sigmoid 

 longitudinal divisions, 2 in 0,oi mm., finely striate; striae 17 in 0,oi mm. V. strongly compressed 

 and elevated, without any junction-line. Striae (at the keel) 12 in 0,oi mm., curved, towards the 

 keel with distant puncta, 8 in 0,oi mm. 



Brackish water (mouths of rivers): Cameroon (Dus^n)! 



3. A. alata Kutz (1844). — Frustule strongly silicious, constricted in the middle. B. 0,04. 

 Junction-line not sinuose, but frequently with a row of large puncta. V. linear, with acuminate 

 ends. L. 0,io to 0,ii; B. 0,02 mm. Median line strongly sigmoid. Basis of the keel linear, sigmoid. 



