130 v. T. CLEVE, SYNOPSIS OF THE NAVICULOID DIATOMS. 



Var. lineata Cl. — L. of V. 0,085; B. 0,oi5 mm. Strice 12 to 13 in 0,oi mm., composed of 

 puncta (about 9 in 0,oi mm.) forming straight, longitudiiial rows. — A. litoralis Cl. M. D. N:o 255. 



Marine: Mouth of Somme! 



Var. minor Grun. (1880). — Frustule elliptical, truncate. L. O, os to 0, 037; B. 0,oi7 to 

 0,0 19 mm. Divisions about 8 in 0,oi mm. Strife 17 in 0,oi mm. — A. D. p. 25. Cl. M. D. N:o 142. 



Marine: West coast of Sweden! 



Var. helgica Grun. (1880). — Frustnle rectangular. L. 0,0 3 3 to 0,04 8; B. 0,021 to 0,022 

 mm. Divisions of tbe zone about 9 in 0, 01 mm. Strise on the zone 18 in 0, 01 mm. Valve with 

 Ifi to 17 finely punctate strife in 0,oi mm. — V. H. Syn. p. 56 V. H. T. JSTio 74. 



Marine: Belgium! 



16. A. Isevis Grbg. (1857). — Frustule hyaline and membranaceous, rectangular, with niore 

 or less truncate ends. L. 0,04 to O 09; B. 0, 02 to 0, 04 mm. Zone witli numerous divisions, 6 to 

 9 in 0,01 mm. Strite fine, about 22 in 0, 01 mm. — D. of Clyde p. 514 Pl. XII f. 74 a, h, c. 

 A. S. Atl. XXVI f. 10. Grun. A. D. p. 24 Pl. I f. 8 (var of A. ostrearia?). Dannf. D. of the 

 Baltic p. 20 Pl. I f 5. 



Brackish and marine: Finmark! North Sea! Balearic Islands! Java (A. S. Atl.). 



A. Icevis diflPers from A. ostrearia by being more transparent and thin. The strise are much 

 more delicate, and scarcely visible on the connecting zone. In some specimens the stauros is only 

 imperfectly developed, in which case A Icevis offers a remarkable likeness to A. lineolata. Akin 

 to A. Icevis is probably A. nohilis Flögel Pommerania Exp. p. 88 f. 9. 



Var. IcBvissima Greg. (1857). — F. very thin. L. 0,o6 to 0,07 6; B. 0,o23 mm. Divisions 

 of the zone obscure. Stria; 27 to 28 in 0,oi mm. — A. Icevissima Greg. D. of Clyde p. 513 Pl XII 

 f. 72. A. S. Atl. XXVI f 3, 13, 14. V. H. T. N:o 8. 



Brackish and marine: Sea of Kära! Finmark! Scotland! England! 



A^ar. minuta Cl. — Frustule in L. about O.035; B. 0, 02 mm. Strife very delicate. — 

 A. Icevissima H. L. Sm. T. N:o 615. 



Marine: Helgoland! 



Var. perminuta Grun. — Frustule in L. 0,oig to 0,oi8; B. 0,oo85 mm. Strife very delicate. 

 — A. Iceviss. var. permin. Grun. in V. H. T. N:o 9. A. Mans Flögel? (Grun.). 



Marine: Swansea Docks, Schleswig (Grun.). 



To A. Icevis seems to belong A. excisa Greg. (D. of Clyde p. 521 Pl. XIII f. 86, 1857) and 

 A. S. Atl. XXXIX f. 3. 



17. A. qiiiitlrata Bréb. (1889). — Frustule very thin and membranaceous, rectangular, with 

 broad, truncate ends. L. 0,oii; B. 0, 03 mm. Stauros narrow. Zone with numerous, strongly 

 marked divisions, about 6 in 0, 01 mm. Stritie exceedingly fine. - • KiiTZ Sp. Alg. p. 94? V. H. 

 Syn. p. 56 Pl. I f 24. A. parallcla Flögel Pommerania Exp. p. 88 f 8 (1873)? A. polysonata 

 Castr. D. of Challenger Exp. p. 8 Pl. XXVII f. 18 (1856)? 



Marine: Belgium (V. H.), Sweden, Fiskebäckskil! 



This species is remarkable for its cell-contents, the chromatophores being numerous rounded 

 discs, aa in the coccocliromatic diatoms. It differs from A. ostrearia. in its rectangular (uxtline 

 and exceedingly fine .structure, and from xi. Iceris in its strongly marked divisions. 



Subgenus Amblyamphora. 



Fi'iistule more or less rectangular. Connecting zone complex. Valves iinear to lunate, with 

 fibtuse, Msually liroad ends. Components of the median line divergent towards tlie dorsal margin. 

 Axial and central areas iiidistinct. Structure: fine ])uncta arranged in transvei'se striu'. wliicli 

 011 the \'ciitral sidc iisiialiy di\i'rge towards the median line. No longitndiiial lines. 



