'I 



Central pores approximate ... . . . A. bipunctata Geun. 



— distant — . . . A. zellensis Gbun. , 

 Central area a transverse fascia . . A. Macraeana Pant. 



— — not dilated . . .... . . 8. 



Ends acute ... . . . . . . . A. serians Br^b. 



• — obtuse . . ..... .... 9. 



( Larger forms. L. 0,1 mm. . . . A. polygramma Ehb. 



\ Smaller — L. 0,02 to 0,03 mm. . A. brachysira Gkhn 



1. A. sphserophora Ktixz (1844). — V. elliptic-lanceolate with rostrate-capitate ends. 

 L. 0,055 to 0,08; B. 0,oi7 to 0,02 mm. Axial area narrow, linear. Central area irregularly 

 rounded, larger on one side of the valve than on the other. Striae slightly radiate throughout, 

 16 in 0,01 mm. — Navic. sphcerophora KtJTZ Bac. p. 95 PI. IV, f., 17. "W. Sm. B. D. I PL XVII 

 f. 148. V. H. Syn. p. 101 PL XII f. 2. A. S. Atl. XLIX f. 49—51. 



Fresh or slightly brackish water: Sweden! England! Switzerland! East Indies! New Zealand! 

 Illinois! Guatemala! "West Indies (St. Martin! Jamaica!) Ecuador! 



Var. Uceps Ehb. (1843). — Smaller. L. 0,o4; B. 0,oi3. Striae finer. — Nav. biceps Ehb. 

 Am. p. p. ScHUM. I Nachtr. p. 21 f. 26. A. S. Atl. XLIX f. 52. N. sphceroph. v. minor V. H. 

 Syn. PL XII f. 3. N. sphceroph. subeap. Geun. Foss. D. Ost. Ung. p. 157. 



Slightly brackish water: Franzenbad (Atl.), Eger foss! 



2. A. sculpta Ehb. (1840). — V. lanceolate, with protracted, rostrate, and obtuse ends L. 0,07 

 to 0,i; B. 0,0 25 to 0,0 3 6 mm. Axial area narrow, linear, bordered by a single row of puncta, 16 

 in 0,01 mm. Central area uniting with large, lunate lateral areas, of which one expands in the 

 middle to the margin. Striae 15 to 16 in 0,oi mm., slightly radiate, distinctly punctate; puncta 

 crowded near the margin, distant towards the lateral areas, where they are arranged in oblique, 

 somewhat undulating rows. — Nav. sculpta Ehb. Ber. 1840 p. 18. M. G. X: i, f. 5. Fresenius 

 Senckenb. Abh. IV PL IV f. 14 to 16. A. S. Atl. XLIX f. 46 to 48. V. H. Syn. p. 100 PL XII 

 f. 1. Pant. II, XI f. 191. K rostrata KtJTZ. Bac. p. 94 PL HI f. 45 (1844). Donk. B. D. p. 15 

 PL II f. 9. Grun. Verb. 1860 p. 540. N. tumens W. Sm. B. D. PL XVII f. 150 (1853). 



Brackish water: Baltic! Franzenbad! Mansfelder Seen! Neusiedler See (Grun.), Belgium 

 (V. H.), S:ta Flora (Ehb.), England! Hungary fossil (Pant.), New Zealand! Ecuador! 



Var. major Cl. — L. 0,i2 to 0,i5; B. 0,04 to 0,o5 mm. Lateral areas almost similar. 

 Strise 13 in 0,oi mm. 



Brackish water: S:ta Rosa, Calif. (Grove Coll.)! Guatemala, fossil! 



A. sculpta is nearly akin to A. sphcerophora, from which it is distinguished by larger size 

 and the large, lunate lateral areas, which are in typical specimens somewhat dissimilar, one of 

 them extending in the middle to the margin. A. sculpta is also related to A. polygramma, together 

 with which form it usually occurs, and which differs by its not protracted ends. Both are 

 to be considered as forms of the same species. 



3. A. polygramma Ehb. (1843). — V. narrow-elliptical, with obtuse, not protracted ends. 

 L. 0,08 to 0,13; B. 0,023 to 0,03 mm. Axial area narrow, linear, bordered with a single row of 

 puncta. Central area transverse, uniting with narrow, somewhat asymmetrical lateral areas. Strise 

 about 14 in O.oi mm. very slightly radiate throughout and composed of distant puncta, arranged 

 in longitudinal, undulating rows. — Stauroneis polygramma Ehb. Am. II: 6, f. 30. Nav. costata 

 KtJTZ. Bac. p. 93 PL III f. 56 (1844). N. bohemica Ehb. Mic. G. X: i f. 4 a (1854). Fresenius 

 Senckenb. Abh. IV PL IV f. 10 to 13. A. S. Atl. XLIX f. 43 to 45. N. fossilis Ehb. Mic. G. 

 X: 1, f. 6 (1854). N. pannonica Grun. Verb. 1860 p. 541 PL IV f. 40. N trigramma Fresenius 

 Senckenb. Abh. IV PL IV f. 1 to 9 (1862). 



Brackish water: Sweden! Franzenbad! Eger! Neusiedler See (Crun.), Catania fossil (Grun.), 

 Cuba (Ehb.), Utah! 



