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



Var. Tohyrnyana Grun. (18(50). — Frustule slightly coii.stricted. 1j. 0,065 to 0,08?; Ji. 0,02 to 

 0,02 7 mm. Junction-line slightly sinnose. Valve narrow, linear, with rostrate ends, and almost 

 straight median line. — Grun. Verh. 1860 p. oGn PI. VI f. 0. 



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



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

 England) occurs a form, determined by Grunow as A. Pokorn. L. 0,09; B. 0,04 mm. Striee 

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

 sigmoid. 



Var. puncfulata Grun. (1880). — Frustule slightly constricted. L. 0,03 7 to 0,0 9 5 mm. B. 0,02 

 to 0,02 3 mm. Junction-line not .sinuose, with a row of small puncta. Striae about 27, on the keel 

 24 in 0,01 mm. — A. pal. r. punct. Grin. A. D. p. ij-2, PL IV f. 84. Franz Josephs L. D. p. 53 

 (105), PI. 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,o5 to 0,ii4 mm 

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

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

 A. plieata var. japonica Castr. Challenger Exp. I), p. 40, PI. XXX, f. 8. 



Mai'ine: Atlantic coasts of N. America (Lewis). 



Var. dilatata Pant. (1891). — Frustule strongly constricted. L. 0, 139. Height of the valve 

 0,025; at the constriction 0,oio5 mm. Junction-line crenulated. Strife 25 in O.oi mm. — A. dila- 

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



Brackish water: Hungary, fossil (Pant.). 



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



Var. horcaUs Grun. (1880). — Frustule slightly constricted. L. 0,o79 to 0,o85; B. 0,o28 to 

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

 connecting zone 26 in 0,oi mm. — A. pal. var.? horealis Grun. A. D. p. 62, PI. 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,o4 mm. Junction-line 

 arcuate, not sinuose. Strife very tine. V. narrow, lanceolate, with strongly sigmoid median line. 

 — A. dupl. Donk. T. M. S. VI p. 29, PI. Ill f. 13. — A. pal. v. dupl. V. H. Syn. p. 121, PI. 

 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 EuL. in V. H. Syn. PI. XXII f. 17. 



Brackish water: Cette (Grun.). 



A. pialndosa is a very variable species, closely connected with A. alafa. Nearly akin to 

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

 f. 6) from (Queensland. The fru.stule is deeply constricted. L. 0, 128 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,n 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. Strife (at the keel) 12 in 0,oi mm., curved, towards the 

 keel with distant puncta, 8 in 0,o 1 mm. 



Brackish water (mouths of rivers): Cameroon (Dusi5n)! 



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

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

 ends. L. 0,io to 0, 11; B. 0,02 mm. Median line strongly sigmoid. Basis of the keel linear, .sigmoid. 



