KONGL. SV. VET. AKADEMIENS HANDLINGaB. BAND 27. N:0 3. 129 



side very narrow. Its strige 15 in 0,o: mm. — Hedwigia VI p. 23. M. J. 1877 p. 178 Pl. CXCV 

 f. 9. A. D. p. 25. Icon. n. Pl. IV f. 10. 



Marine: Balearic Islands! Adriatic! China! Honduras (Grnn.), Barbados! 



Var. hriocensis Leud. Fortm. Ms. — Frustule elliptical, witli truncate ends. L. 0,o4r); 

 B. 0,02 mm. Zone with abont 8 divisions in 0,oi mm. transversely striate; strise 15 in 0,0 1 mm. 

 Dorsal obliqvie stricE 21 in 0,oi mm. — Pl. IV f. 11. 



Marine: The Eng. Cbannel (Deby Coll.)! 



13. A. Lunula Cl. N. Sp. — V. lunate, with subactite ends and straigbt ventral margin. 

 L. 0,13 to 0,15; B. 0,018 to 0, 02 mm. Median line straight, not very closely approximate to the 

 ventral margin. Central nodule transversely dilated into a stauros. Striae on the dorsal side 

 almost parallel, 14 to 17 in 0, 01 mm., composed of distinct puncta, abont 13 in 0, 01 mm. Ventral 

 side striate; strife 12 to 15 in 0,oi mm. punctate. — Pl. IV f. 13. 



Marine: Balearic Islands! Sumatra (Deby Coll.)! Colon (Deby Coll.)! 



14. A. stauropliora (Castr. 1886?) Cl. — Frustide hyaline, in ontline qnadrate to ree- 

 tangnlar. V. slightly indented in the middle of the dorsal margin, narrow, with obtuse ends. 

 L. 0,05 to 0,055; B. 0,01 mm. Median line straight, at sonie distance from the ventral margin. 

 Central nodule dilated to a transverse stauros. Strise delicate, punctate, about 20 in 0, 01 mm. — 

 A. sp. A. S. Atl. XXV f. 85, 86. A. stawo^yJiora Castr. Voyage Challenger p. 20 Pl. XXVII f. 6? 

 Icon. n. Pl. IV f. 33, 34. 



Marine: Davis Straits (Atl.), North Sea (Atl.), Morocco! Balearic Islands! Pensacola! 

 This form is only imperfectly known and requires further investigations. 



15. A. ostrearia Bréb. (1849). — Frustule silicious, in outline elliptical to qnadrate, or 

 rectangular. Zone with numerous divisions, 3 to 9 in 0,oi mm., distinctly striate. V. of various 

 apparent shapes, depending on its positions. L. 0, 03 to 0,17; B. 0,oo5 to 0, 02 mm. Median line 

 biarcuate. Central nodule transversely dilated to a staixros. Dorsal and ventral side with about 

 equinumerous, distinctly punctate strise, 10 to 17 in 0, 01 mm. 



A. ostrearia is very variable in size and in the number of strise. The valves have very 

 different shapes in different positions, and for these reasons a large number of forms have been, 

 often in a very incomplete manner, described or figured as distinct species. 



Var. vitrea Cl. (1868). — L. of frustule 0,o86 to 0,i; B. 0,068 mm. Zone with 4 to 5 divi- 

 sions in 0,01 mm. its strise 10 to 11 in 0, 01 mm. Strise on the dorsal and ventral side 9 to 10 

 in 0,01 mm. composed of puncta, about 10 in 0, 01 mm. — A. vitrea Cl. Svenska och N. D. p. 237 

 Pl. IV f. 5. A. S. Atl. XXVI f. 25. A. Nova Caledonica Grun. A. S. Atl. XXVI f. 16 (1875). 

 A. Porcellus KittoxV A. S. Atl. XXXIX f. 15 to 17. A. Treuhii Leud. Fortm. D. de la Malaisie 

 p. 11 Pl. I f . 7 (1892)? 



Marine: Spitsbergen! Bohuslän! Mediterranean Sea! Labnan! Japan (Atl.), New Caledonia 

 (Atl.), West Indies! 



Var. typica Cl. — Frustule 0,035 to 0,o8 mm. in length and 0,02 to 0,o6 mm. in breadth. 

 Zone with 3 to 5 divisions in 0,oi mm. Its strise about 13 in 0,oi mm. Strise of the valve 11 

 to 13 in 0,01 mm.; their puncta about 12 in 0,oi mm. — A. ostrearia KtJTz Sp. Alg. p. 94. Grdn. 



A. D. p. 25. A. S. Atl. XXVI f. 23. V. H. Syn. p. 55 Pl. I f. 25. A. membranacea W. Sm. 



B. D. I p. 20 Pl. II f. 29 1853 (strise are statecl to be 31 in 0,oi mm., biit are distinct on the 

 figure at an enlargement of 400 only). A. qtiadrata Bréb. Ktltz Sp. Alg. p. 95 (1849)? A. elegans 

 Greg. t. M. S. v p. 70 Pl. I f. 30 (1857)? A. litoralis Donk. T. M. S. VI p. 30 Pl. III f. 15 

 (1858). A. Petitii Temp. and Brun D. foss. du Japon p. 15 Pl. IX f. 16 (1889). A. Nova Caledo- 

 nica Pant. III Pl. XV f. 227 (1893). 



Marine: Finmark! North Sea! Mediterranean Sea! Sumatra! Labnan! China (Deby Coll.)! 

 Japan (Brun. Coll.)! 



K. Sv. Vet. Akad. Handl. Band 27. N:o 3. 17 



