118 p. T. CLEVE, SYNOPSIS OF THE NAVICULOID DIATOMS. 



^f. I Median line approximate to the ventral margin A. Lagerheimii Cl. 



' \ — — distant from _ _ _ . . . . . . A. cestuarii Cl. 



^^ f Frnstule almost orbicular .... . . . . . . . A. Szaboi Pant. 



\ — elongate-elliptical .... .... 17. 



.„ j L. 0,02 to 0,035 mm . . . . . A. Normani Eabh. 



\ L. 0,05 to 0,085 mm. . . . . A. commutata Geun. 



^„ j Frnstule orbicular 19. 



\ — elongated 30. 



.-„ f L. 0,03 mm. . . ... A. turgida Gebg. 



\ L. 0,045 to 0,08 mm. .... . .... A. costata W. Sm. 



{Strise 7 to 9 in 0,oi mm. . . . 21. 

 — 9 to 13 — — . . 23. 

 — 13 to 20 — — . 24, 



„.. I Strise indistinctly punctate . A. Terroris Ehb. 



I — distinctly — . A. Eunotia Cl. 



„_ J Zone with longitudinal rows of coarse puucta .... . . A. granulata Gebg. 



\ — transversely striate ... . .... ... 23. 



„„ f L. 0,026 to 0,04 mm . . .A. exigua Greg. 



L. 0,04 to 0,12 mm. . . . . A. macilenta Greg. 



Zone with faint divisions . . . .... A. Normani Babr. 



— — distinct — 25. 



35. i' 



„, , Zone delicately striate . . -A. coffceiformis Ag. 



' ' \ — distinctly — . . . . . . A. acutiuscula KiJiz. 



1. A. SBStuarii Cl. (1894). — Prustule elliptical, with broad, truncate ends. L. 0,05; 

 B. 0,03 mm. Zone apparently smooth, with 4 to 5 broad divisions. V. lunate, acute, with 

 somewhat gibbous ventral margin. Median line arcuate in the middle of the valve. Axial area 

 broad, on the dorsal side frequently dilated around the central nodule. Dorsal side with 14 not 

 distinctly punctate, strise in 0,oi mm., not crossed by a longitudinal line. Ventral side broad, 

 with a median row of short strise, about 17 in 0,oi mm. — Diatomiste II p. 146 PI. IX f. 10, 11. 



Brackish water (mouth of rivers): Africa, Cameroon! 



This species which resembles in the outline A. sulcata or A. truncata is remarkable for its 

 very broad, ventral side, in which characteristic it agrees with Cymbella. 



2. A. Lagerheimii Cl. (1894). — Frnstule elliptical, with broad, truncate ends. L. 0,o5 

 to 0,0 7 mm. Zone with about 4 punctate (puncta 16 in 0,oi mm.) lines (divisions) in 0,oi mm. 

 Valve lunate, gradually tapering from the middle to the narrow ends. Dorsal margin arcuate; 

 ventral straight. Median line near the ventral margin. Axial area very large, apparently scabrous. 

 Dorsal side at the margin with a short stauros, reaching to the area, and marginal strise, 12 in 0,oi 

 mm. Ventral side smooth, except at the margin, where are short strise, 16 in 0,oi mm. (perhaps 

 belonging to the zone). — Diatomiste II p. 99 PI. VII f 2. 



Fresh water, moist rocks: Ecuador, Banos! 



This is a very curious species, remarkable for the short dorsal stauros. There is no nearly 

 akin form, as far as I know. Perhaps it is most nearly related to A. veneta, through different 

 in most respects. 



3. A. veneta K©tz (1844). — Frustule elliptical with rounded truncate ends. L. 0,02 to 

 0,06; B. 0,011 to 0,018 mm. Zone with several distinct divisions, about 12 in 0,oi mm., which 

 are more or less distinctly, transversely striate; strise 26 or more in 0,oi mm. V. with convex 

 dorsal and straight or slightly concave ventral margin. Ends subacute, not protracted or rostrate. 

 Central nodule strong, elongated. Median line straight close to the ventral margin; its central 

 pores distant. Dorsal side striate, ventral not. Dorsal strise 20 in O.oi mm., more distant in the 

 middle, pilnctate. — Bac. p. 108 PL III f. 25. V. H. Syn. p. 58 PI. I f. 17. A. fasciata Ehb. 

 1840 (according to H. L. Smith). A. Uohenackeri Eabenh. Siiss. D. p. 31 PI. IX f. 11 (1853). 

 A. quadricostata Eabh. Slissw. D. PI IX f. 5 (1853). A. S. Atl. XXVI f. 74 to 80. A. tumidula 



