104 p. T. CLEVE, SYNOPSIS OF THE NAVICULOII) DIATOMS. 



A. robusta is nearly related to A. Froteus and differs principally by the coarse striae and 

 larger size. A. oblonga Greg. (D. of Clyde p. 515 PI. XIII f. 78) seems to be a form of A. robust n, 

 bnt I have never met with any perfectly similar form. 



10. A. javanica A. S. (1875). — Frustnle rectangular, about three times longer than broad. 

 L. 0,04 5 to 0,06; B. 0,0 17 to 0,02 mm. Zone not complex. Axial area narrow, dilated on the 

 dorsal side around the central nodule. Keel or longitudinal line on the dorsal side very distinct. 

 Strite 12 in 0,oi mm. composed of elongated distant puncta. Ventral side striate, except in the 

 middle. StriiE 12 in 0,oi mm. curved, composed of some few elongated, large puncta or crossed by 

 an undulating narrow line. — Atl. XXVII f. 27, 30 to 33. 



Marine: Java! 



This form is very nearly akin to A. arenicola, of which it niay be a variet3^ 



11. A. arenicola Grun. (1882). — Frustule nearly rectangular, three times longer than 

 broad. L. 0,0.38 to 0,07; B. 0,oi7 to 0,021 mm. Valve in breadth (),oi mm., linear, with broad, 

 unilaterally rounded ends. Median line slightly biarcuate, distant from the ventral margin. Axial 

 area indistinct on the dorsal side. Central area none or orbicular. Dorsal side with 10 to 14 

 coarsely punctate, not interrupted, striae in (),oi mm. Longitudinal line indistinct. Ventral side 

 broad, with radiate, coarsely punctate strite, sometimes crossed by a narrow, blank band. — A. 

 marina rar. arenicola Grun. in CI. M. D. N:o 310. A. marina Pritch Inf. PI. V f. 59? A. arenic. 

 Icon. n. PI. IV f. 19, 20. 



Marine: Coasts of England and Belgium! China (Deby Coll.)! 



Var. major Cl. — V. in L. 0,i; in B. 0,o26 mm. Stria;', 8 to 9 in 0,oi mm. composed of 

 large, distant puncta. — A. robusta A. S. Atl. XXVII f. 39 to 41. A. Lima Pant. Ill PI. XXIII 

 f. 347 (1893). 



Brackish water: Baltic! 



Var. oculafa Cl. — Frustule in L. 0,07; in B. 0,o36 mm. (-entral area on the dorsal side 

 large, rounded. Strife 11 in 0,oi mm. composed of large, distant puncta. — PI. IV f. 21. 



Marine: Sebastopol! 



Var. subcequalis Cl. — Frustule linear elliptical. L. 0,075; B. 0,032 mm. Median line bi- 

 arcuate, very distant from the ventral margin, so that the ventral side is almost as broad as the 

 dorsal. Dorsal side with 10 stria? in 0,oi mm., composed of large puncta, 10 in 0,oi mm. Ventral 

 side entirely covei'ed with coarsely punctate striae. — PL IV f. 22. 



Marine: China (Deby Coll.)! 



12. A. ovalis Kutz (1833). — Frustule broadly elliptical, with truncate ends. L. 0,oi to 

 0,06; B. 0,0045 to 0,033 mm. Valve lunate with subacute ends. Median line slightly biarcuate. 

 Axial and central areas on the dorsal side indistinct or distinct. Dorsal side twice as broad as 

 the ventral. Ventral side with a row of short strise. Dorsal part with 10 to 16 striae in 0,01 

 mm. Strife punctate, not interrupted, or crossed by a somewhat irregular blank band. 



Forma typicu. Frustule in L. 0,o4 5 to 0,ofi; B. 0,024 to 0,033 mm. No axial and central 

 area, no longitudinal band on the dorsal side. Striaj 10 to 11 in 0,oi mm. composed of distinct 

 puncta (about 9 in 0,oi mm.). — A. ovalis KtJTZ Syn. f. 5, 6. Bac. p. 107. V. H. Syn. p. 59 

 PI. I f. 1. H. L. Sm. Types N:o 40. 



Fresh water: Sweden! England! France! Germany! Switzerland (Brun), Baltic (Gulf of 

 Bothnia!) Australia, Lake Muir! 



Var. (jracilis Ehb. (1843). — As the type, but smaller. L. 0,027; B. 0,oi mm. Striae about 

 12 in 0,01 mm. — A. (jracilis Ehb. Am. p. 122 PI. Ill: i f. 43. A. oralis var. (/r. V. H. Svn. ]). 59 

 PI. I f. 3. A. S. Atl.' XXVI f. 101. 



Fresh water: Belgium (V. H.), Harz (Atl.). 



Var. libyca Ehb. (1840). — V. lunate. Tj. 0,o55 to 0,o8; B. O,oii to 0,017 mm. Median line 

 slightly biarcuate. Central area distinct on tlic dor.^al si(h\ frc(|iiPiitly miiting with an irregular, 



