188 r. T. CLEVK, SYNOPSIS OF THE NAVICULOII) DIATOMS. 



jirtificial key. 



A. trinodis Arn. 



2. 



erse fascia '6. 



' 4. 



_. j Valve biconstricted . . . 



\ — not constricted . . 

 y j Lower valve witli a transv 



I — — without . . . 



j Valve narrow, linear-lanceolate A. affinis Grun. 



3. •! — narrow, elliptical A. hungarica Grun. 



( — elliptical, rostrate A. cxigua Grun. 



. j Valve broad and short h. 



\ — narrow and elongated 7. 



^ ( Strise fine {2b in 0,oi mm.) A. Binsolrttiana KiJTZ. 



' \ — coar.se (10 to 14 in O.oi mm.) 6. 



I Valve broadly lanceolate A. delicatula Kijiz. 



I — elliptical A. Haurkiana Grun. 



„ I Stria 12 to 16 in 0,01 mm 8. 



'■ \ — 21 or more U. 



,, I Valve lanceolate A. Hudsonis Grun. 



o. 



I Valv 



linear A. glahrata Grun. 



,j ) Striae 21 in 0,(U mm A. exilis Kiiiz. 



\ — 24 or more in 0,oi mm 10. 



^ ) V^alve with parallel margins 11. 



\ — — slightly convex 12. 



^ ) Fresh water habitat A. linearis W. Sm. 



\ Marine A. tceninta Grun. 



... j Ends subcapitate A. microcephala KtJTZ. 



\ — obtuse A. minutissima KtJTz. 



1. A. niinutissini.'i Kutz. (1833). — Linear with somewhat attenuate and obtuse ends. 

 L. O.oi.T to 0,02; B. 0,003 to 0,004 mm. Upper V. with narrow, linear axial area. Stria about 

 26 ill 0,0 1 mm. parallel. Lower V. without axial area and with small, transverse central area. 

 Strite about 2.") in 0,oi mm., stronger in the middle, slightly radiate. — Dec. N:o 75 (1833) accor- 

 ding to Lagst. Grun. A. D. p. 23. V. H. Syn. p. 131 PI. XXVII f. 35 to 38. A. exilis W. Sm. 

 B. D, II PI. XXXVII f. 303, 



Fresh water: Sweden! Germany! England! Belgium (V. H.), probably common everywhere. 

 Var. cryptoccpJutlu Grun. — Smaller, with slightly capitate ends. L. 0,012 to0,oi8; B. 0,002 

 to 0,003 mm. Strife about 30 in 0,oi mm. — V. H. Syn. PI. XXVII f. 41 to 44. 

 Fresh water: Finland! 



2. A. microcephala Kutz. (1844). — Linear lanceolate, with subcapitate ends. L. 0,o()'.» 

 to (),02(>; B. 0,003 mm. Upper valve with linear axial area and parallel strise, 30 — 3(> in 0,oi mm., 

 the median strict abbreviated. Lovi'er V. without axial area aiul with small transverse central 

 area. Strise about 32 in 0,oi mm. slightly radiate. — A. mirrocephalmn KiiTZ. Bac. 7.") PI. Ill 

 f. 13, 19 (1844). Grun. A. D. p. 22. V. H. Syn. p. 131 PI. XXVII f. 20 to 23. Navicala 

 pachijciphala ScHUM. Preuss. I). 2:te N. II f. 44? 



Fresh water: Sweden (Helsingland)! Belgium (V. H.). 



Achnanthidium microcephalum W. Sm. B. i). is probably Anomoeoneis exilis Grun. 



3. A. linearis W. Sm. (1855). — Linear with rounded ends. \j. 0,oi tu 0,02; B. 0,oo:i to 

 0,004 mm. Upper V. with narrow, linear axial area and parallel striae, 24 to 27 in 0,oi mm. 

 Lower V. without axial area and with small and transverse central area. Striae. 22 to 28 in O.oi 

 mm. — Achnanthidium lin. W. Sm. Ann. and Mag. Nat. Hist. 1855 p. 8 PL I f. 9. B. i). 11 

 p. 31 PI. LXI f. 381. Achnanthes lin. Grun. A. D. p. 23. V. H. Syn. p. 131 PI. XXVII f. 31,32. 



Fresh water: Norway (Dovre)! England! Belgium (V. H.). 



