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



side very narrow. Its striae 15 in 0,oi mm. — Hedwigia VI p. 23. M. J. 1877 p. 178 PI. CXCV 

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



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



Var. hriocensis Lbud. Fortm. Ms. — Frustule elliptical, with truncate ends. L. 0,04 5; 

 B. 0,02 mm. Zone with about 8 divisions in 0,oi mm. transversely striate; striae 15 in 0,oi mm. 

 Dorsal oblique striae 21 in 0,oi mm. — PI. IV f. 11. 



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



13. A. Lumila Cl. N. Sp. — V. lunate, with subacute ends and straight ventral margin. 

 L. 0,13 to 0,15; B. 0,018 to 0,o2 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,oi mm., composed of distinct puncta, about 13 in 0,oi mm. Ventral 

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



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



14. A. staurophora (Caste. 1886?) Cl. — Frustule hyaline, in outline quadrate to rec- 

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

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

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

 A. sp. A. S. Atl. XXV f. 85, 86. A. staurophora Castr. Voyage Challenger p. 20 PI. XXVII f. 6? 

 Icon. n. PI. 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 Br^b. (1849). — Frustule silicious, in outline elliptical to quadrate, 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 stauros. Dorsal and ventral side with about 

 equinumerous, distinctly punctate striae, 10 to 17 in 0,oi mm. 



A. ostrearia is very variable in size and in the number of striae. 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 0,086 to 0,i; B. 0,068 mm. Zone with 4 to 5 divi- 

 sions in 0,01 mm. its striae 10 to 11 in 0,oi mm. Striae on the dorsal and ventral side 9 to 10 

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

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

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

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



Marine: Spitsbergen! Bohuslan! Mediterranean Sea! Labuan! 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 striae about 13 in 0,oi mm. Striae of the valve 11 

 to 13 in 0,01 mm.; their puncta about 12 in 0,0 1 mm. — A. ostrearia KtJTz Sp. Alg. p. 94. Grun. 



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



B. D. I p. 20 PI. II f. 29 1853 (striae are stated to be 31 in 0,oi mm., but are distinct on the 

 figure at an enlargement of 400 only). A. quadrata BriSb. Ktitz Sp. Alg. p. 95 (1849)? A. elegans 

 Greg. T. M. S. V p. 70 PL I f. 30 (1857)? A. litoralis Done. 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. Ill PL XV f. 227 (1893). 



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



Japan (Brun. Coll.)! 



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



