KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND. 27. N:0 3. 117 



32. A. margaritifera Cl. N. Sp. — Frustule indented in the middle, bicuneate, with broad, 

 truncate ends. L. 0, 027 to 0,04; B. 0, 015 mm. Zone witli about 4 divisions in 0, 01 mm. coarsely 

 transversely striate. Strise 8 in 0, 01 mm., composed of distinct puncta. V. with arcuate dorsal, 

 slightly convex ventral margin, and rostrate ends. L. 0,035; B. 0, 01 mm. Median line straigbt. 

 Longitudinal line indistinct. Central nodule not stauroid. Axial area indistinct; central small 

 rounded. Dorsal strife 8 in 0,oi mm., composed of a few large puncta, crossed by a broad, blank 

 area. Ventral side with a row of small puncta along the margin (10 to 11 in 0,oi mm.). — 

 Pl. III f. 30, 31, 



Marine: Galapagos Islands! 



Subgenus Halamphora Cl. 



Frustule elongated, sometimes constricted in the middle. Connecting zone complex. Valve 

 boat-shaped, usually with rostrate or capitate ends. Median line close to the ventral margin. 

 Axial area usually indistinct. No longitudinal line on the dorsal or ventral side. Structure: 

 puncta disposed in transverse strise. 



This subgenus, to which belongs A. salina of W. Smith, comprises a large number of 

 forms, closely connected in part. They differ from Cymbatnphora by the zone being complex, by 

 the, usually, capitate ends and the distinctly punctate strife. The small terrestrial Ä. Normani 

 seems to be related to A. perpusilla of the subgenus Amphora, so also A. veneta and A. commu- 

 tata, otherwise there is no close connection between this and any other group of Amphora. 



Artificial key. 



i Strise crossed by a longitudinal band A. intersecta A. S. 



1. < — — by several — blank lines A. czekehazensis Pant. 



( — not — — — 2. 



„ j Strise with distant puncta 3. 



I 



Dorsal margin slightly triundulate A. Grunoivii A. S. 



— — not undulate A. corpiilenta Cl. a. Gkovb. 



Valve constricted 5. 



closely punctate 4. 



Dorsa 



*• 1 - not - 11. 



[ Valve with one constriction 6. 



5. < — — two constrictions A. Jeschkei Jan. 



( — — several — 10. 



„ j Zone on the dorsal side reticnlate A. Peragalli Cl. 



{■ 



— not — 7. 



„ I Constriction with a median gibbosity A. bullata Cl. 



\ — withont — — 8. 



Divisions of the zone faint A. bigibba Geun. 



distinct 9. 



. . Dorsal strise about 13 in 0,0 1 mm A. trinodis Gebg. 



9 to 10 — — A. angularis Gebg. 



..„ / Undulations equal A. tetragibba Cl. 



\ Median undnlation larger than the others A. sarniensis Geev. 



Strise 5 in 0,0 1 mm A. clara A. S. 



— 9 to 10 in 0,01 mm 12. 



..„ I Ends of the valve not capitate 13. 



capitate, not curved inwards 18. 



u.j 



{ 



..„ I Ends not rostrate 14. 



1 — rostrate, curved inwards 16. 



... ( Strise 20 in 0,oi mm A. veneta KiJTz. 



I — 12 to 14 in 0,01 mm 15. 



