YEGA-EXPBDITJONENS VBTSNSKAPLIa A ABBETBN. 467 



metric, others not. There are also closely allied forms, which 

 have arcuate valves and therfore belong to RhoiJconeis. The 

 Rh. BoUeana Grun. is really nearly allied to the group of Nav. 

 directa. Although all the forms of this section in my opinon 

 are nearly allied, it may be necessery to name them and 

 arrange them. 



To N. directa I refer all slender, or almost linear forms, 

 about 10 times longer than broad, which have parallel strise, 

 shortened around the central nodule. 



v&r. remota Grun. (A. Schm. Atl. PI. XL'VII, fig. 2) striae 4 

 — 5 in 0,01 mm. — Finm., Spitsb., Kara (Matotschkin Schar). 



var. Incus Grun. (A. Schm. Atl. PI. XLVII, fig. 7 from the 

 Mediterranean Sea) Strise 4 in 0,oi mm. very slightly radiant, on 

 one half of the valve interrupted. I have not seen typical 

 specimens from the Arctic Sea. 



var. angusta Grun. (A. Diat. pag. 39) strise 8 in 0,oi mm. 

 Greenl. (Mushroom Point), Finm., Spitsb., Kara, Cape Deschnew 

 (East Cape). Seems to me to be the typical iV. directa W. Sm. 



var. suUilis Greg. (Pinnul. ? subt. Greg. D. of CI. pag. 488, 

 PL IX, fig. 19) strise 9—11 in 0,oi mm. Spitsb., F. J. L., Cape 

 Deschnew (East Cape), Cape Wankarema. 



var.? decussafim-striata Grun. — F. J. L. (unknown to me). 



N. transitans CI. — Intermediate forms between N. directa 

 and N. Zostereti Grun. Valves more or less abbreviate, lan- 

 ceolate. Strise parallel or slightly radiant. 



forma genuina. — 6 to 4 times longer than broad, lanceolate. 

 Strise coarsely lineate, 8 in 0,oi mm. almost parallel, shortened 

 around the central nodule. Length 0,o65 to 0,09 mm. Breadth 

 0,016 mm. to 0,02 mm. — Cape Wankarema. — PI. 36, fig. 31 

 and 33. 



var. derasa Grun. (Nav. derasa Grun. A. Diat. pag. 39, 

 PI. II, fig. 46). Strise on both sides of the median line inter- 

 rupted by a linear area, 8 ^'2 — 12 in 0,oi mm. in the middle, 

 10 — 14 near the ends, not so strongly transversely lineate as 

 in typical specimens, (according to Grunow the strise are 10 

 in 0,01 mm. in the middle and 16 at the ends). Length 0,067 

 mm. Breadth 0,oi5 mm. — Kara, Cape Wankarema-, Cape 

 Deschnew (East Cape). 



forma minuta. — Strise 12 in 0,oi mm., distinctly trans- 

 versely lineate. Length 0,035 mm. Breadth 0,oi2 mm. — Cape 

 Deschnew (East Cape). PI. 36, fig. 37. 



form, gracilenta Grun. 1. c. Kara. 



N. incudiformis Grun. (N. Incus abbreviata Grun. A. Diat. 



