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



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

 L. 0,05 to 0,0 8 mm. Zone with numerous divisions. Valve semicircular with straight ventral 

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

 n 0,01 mm. — Bac. p. 108 PL XXX f. 18. W. Sm. B. D. I PI. 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 (Grun.). 



4. A. bacilliiris Greg. (1857). — Frustule almost rectangular. L. 0,05; B. 0,oi7 to 0,0 2 

 mm. Zone with 7 divisions in 0,oi mm. transversely striate; strife 20 in 0,oi mm. Valve narrow. 

 Central nodule not dilated into a stauros. Striae radiate, 18 to 19 in O.oi mm. not crossed by a 

 longitudinal line. — D. of Clyde p. 527 PI. XIV f. 100. Icon. 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 Gregory's A. hacillaris. As I have seen no detached 

 valves, I have not been able to give a complete description, for which reason this species requires 

 a more accurate examination. 



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

 ends. L. 0,o5 to 0,08; B. 0,032 to 0,04 mm. Zone with numerous divisions, 5 to 6 in 0,oi mm., 

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

 number on the dorsal and ventral side, distinctly punctate. 



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

 moderately coarse puncta. — A. arcus Greg. 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). — Striae 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,oi mm., forming undulate, longitudinal lines. 

 — A. sulcata A. S. Atl. XXVI f. 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 6), 

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



(J. A. rhombica Kitton (1876). — V. semi-rhomboidal, apiculate. L. 0,i3to0,26; B. 0,02i 

 to 0,0 5 mm. Median line closely approximate to the ventral margin. Striae 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; 

 striae a little closer (11 to 13 in 0,oi 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,i4; B. 0,024 mm. Dorsal striae 16 to 17, ventral 

 18 in 0,01 mm. 



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



Var intermedia Cl. — L. 0,09 to 0,i ; B. 0,oi7 mm. Dorsal striae 14 and ventral 16 in 0,oi mm. 



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



7. A. maeandrina Cl. N. Sp. — V. lunate, apiculate. L. 0,i8; B. 0,o35 mm. Central 

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

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

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



Marine: Colon (Deby CoU.)! 



