104 p. T. CLEVE, SYNOPSIS OF THE NAVICULOID BIATOMS. 



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

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

 but I have never met with any perfectly similar form. 



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

 L. 0,04 5 to 0,06; B. 0,oi7 to 0,o2 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. 

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

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

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



Marine: Java! 



This form is very nearly akin to A. arenicola, of which it may be a variety. 



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

 broad. L. 0,o38 to 0,o7; B. 0,oi7 to 0,o2i mm. Valve in breadth 0,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 0,oi mm. Longitudinal line indistinct. Ventral side 

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

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

 Icon. n. PL 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. Striae 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. oculata Cl. — Frustule in L. 0,07; in B. 0,036 mm. Central area on the dorsal side 

 large, rounded. Striae 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,o32 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 striae in 0,oi mm., composed of large puncta, 10 in 0,oi mm. Ventral 

 side entirely covered with coarsely punctate striae. — PL IV f. 22. 



Marine: China (Deby Coll.)! 



12. A. ovalis KtJTZ (1833). — Frustule broadly elliptical, with truncatp 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 striae. Dorsal part with 10 to 16 striae in 0,oi 

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



Forma typica. Frustule in L. 0,04 5 to O,ofi; B. 0,o24 to 0,o33 mm. No axial and central 

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

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

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

 12 in 0,01 mm. — A. gracilis Ehb. Am. p. 122 PL III: i f. 43. A. ovalis var. gr. V. H. Syn. p. 59 

 PL I f. 3. A. S. Atl. XXVI f 101. 



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



Var. libyca Ehb. (1840). — V. lunate. L. 0,055 to 0,o8; B. 0,oii to 0,oi7 mm. Median line 

 slightly biarcuate. Central area distinct on the dorsal side, frequently uniting with an irregular, 



