KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 27. N:0 3. 127 



3. A. hyalina Kutz (1844). — Frustule membranaceous, more or less orbicular in outline. 

 L. 0,05 to 0,08 mm. Zone witli niimerons divisions. Valve semicircular with straight ventral 

 margin and somewhat apiculate ends. Median line clnse to the ventral margin. Striae about 23 

 n 0,01 mm. — Bac. p. 108 Pl. XXX f. 18. W. Sm. B. D. I Pl. II f. 28. A. S. Atl. XXVI f. 52 

 to 55. A. hemisphcerica Grun. in Hedwigia VI p. 24 (1867). 



Marine: Spitsbergen! North Sea! Mediterranean Sea! Adriatic! Cape May! Barbados! Hon- 

 duras (Grrun.). 



4. A. bacillaris Greö. (1857). — Frustule almost rectangular. L. 0,05; B. 0,oi7 to 0,02 

 mm. Zone vs^ith 7 divisions in 0, 01 mm. transversely striate; strite 20 in 0,oi mm. Valve narr ow. 

 Central nodule not dilated into a stauros. Strise radiate, 18 to 19 in 0, 01 mm. not crossed by a 

 longitudinal line. — D. of Clyde p. 527 Pl. XIV f. 100. leon. n. Pl. IV f. 40, 41. A. bac. var 

 scotica Cl. M. D. N:o 310. 



Marine: Coasts of Scotland! 



This form agrees pretty well with Grb60Ry's A. hacillaris. As I have seen no detached 

 valves, I liave not been able to give a complete description, for whicli reason this speeies requires 

 a more accurate examination. 



5. A. arcus Greg. (1854). — Frustule more or less elliptic-rectangular, with broad, truncate 

 ends. L. 0,05 to O, os; B. 0,032 to 0, 04 mm. Zone with numex'ous divisions, 5 to 6 in 0,oi mm., 

 which are transversely striate. V. narrow, lunate, acute. Median line biarcuate. Striee of equal 

 number on the dorsal and ventral side, distinctly punctate. 



Forma typica Cl. — Strise of the zone 10, of the valve 9 to 10 in 0, 01 mm. composed of 

 moderately coarse puncta. — A. arcus Greu. T. M. S. V. p. 75 Pl. I f. 37. D. of Clyde p. 522 

 Pl. XIII f. 88. Icon. n. Pl. IV f. 4. 



Marine: Spitsbergen! Finmark! Scotland! Sumatra (Deby Coll.)! Japan, fossil (Brun). 



Var. sulcata A. S, (1875). — Stria; of the zone 16 to 20 in 0,oi mm., of the valve 14 to 20 

 in 0,0 1 mm. finely punctate; puncta about 25 in 0, 01 mm., forming undulate, longitudinal lines. 

 — A. sulcata A. S. Atl. XXVI i. 46, 47. 



Marine: Rovigno, Adriatic! Hembang Bay (Deby Coll.)! Barbados (Cl. M. D. N:o 149). 



The variety sulcata is akin to A. lineolata but more silicious and connected with the type 

 by intermediate forms. It cannot be A. sulcata Greg. D. of Clyde (p. 523 Pl. XIII f. 92 and 92 b), 

 which seems to represent some form of A. Grevilleana and has much broader divisions. 



6. A. rhombica Kitton (1876). — V. semi-rhomboidal, apiculate. L. 0,i3to0,26; B. 0,021 

 to 0,0 5 mm. Median line closely approximate to the ventral margin. Strise on the dorsal side 10 to 

 12 in 0,01 mm., radiate, frequently alternately longer and shorter near the dorsal margin, composed 

 of elongated puncta, forming undulate, longitudinal lines. Ventral side very narrow, striate; 

 strise a little closer (11 to 13 in 0, 01 mm.) than on the dorsal side. — A. S. Atl. XL f. 39. 



Marine: Mediterranean Sea (Perag.), Island of Rhea! Sumbava (Kinker Coll.)! Sumatra 

 (Deby Coll.)! Macassar Straits (Grove Coll.)! China! Colon (Deby Coll.)! 



Var. gracilior Cl. — V. in L. 0,ii to 0,14; B. 0,024 mm. Dorsal striee 16 to 17, ventral 

 18 in 0,01 mm. 



Marine: Tahiti! Campeachy Bay (Brun Coll.)! 



Var intermedia Cl. — L. 0,o9 to 0, 1 ; B. 0,oi7 mm. Dorsal strise 14 and ventral 16 in 0, 01 mm. 



Marine: Gette (Temp., Perag. Types N:o 447). 



7. A. niaBaudrina Cl. N. Sp. — V. lunate, apiculate. L. 0,i8; B. 0,035 mm. Central 

 nodule strong. Median line close to the ventral margin. Dorsal part with about 12 strise in 0, 01 

 mm. composed of distant, elongated pxxncta, about 5 to 6 in 0, 01 mm., forming undulate, longi- 

 tudinal rows. Ventral part narrow, with 19 to 20 transverse strise in 0,oi mm. — Pl. IV f. 14. 



Marine: Colon (Deby Coll.)! 



