160 r. T. CLRVE, SYNOrSIS OF THE NAYICULOID DIATOMS. 



Median strife more distant than the others 50 



49. . 



— not — — — C. incerta Grun. 



{ 



J... j Central area dilated to the ventral margin C. sinuata Greg. 



" I — — not — — — C. (pqualis W. Sm. 



r, ( Valve almost symmetrical 52. 



51 , . , , ■ 



^„ I Central area 1 



\ — — SI 



— decidely asymmetriral > 53. 



Central area large C. MoUerinna Grun. 



small C. lanisfris AG. 



j.„ j Axial area narrow 54. 



I — — moderately liroad 5G. 



J. . ( Length about t),o:! to 0,04 mm 55. 



' \ — — l',iii; to 0,07 mm C. horealin Ci,. 



.,, j Stria> 5 in 0,iii mm C. alpino (iRUN. 



" \ — about 10 in 0,oi mm C\ (pqualis W. Sm. 



J. r, I Axial area dilated to a small central area 57. 



■' ' t — — not — — — - 58. 



Stria! coarsely ])unctate C. Hcmckii V. H. 



„ I Stria; c 

 •"• 1 - ii 



finely — C. Reinhardtii Grun. 



^ j Length about 0,03 mm C. leptoceros Grun. 



\ — — ••,oc mm C. nusfriaca Grun. 



^,, j Median ventral stri.-e ending in isolated puncta C. fumhJula var. .srilmormn. 



■'■ ' \ — — — not (50. 



,.,, ( Terminal nodules distant from the ends (J. Ce.sntii Rabh. 



01). < 



I — — ai)j)roximate to — ()1. 



... j Median line straight, strongly excentric 62. 



\ — — subarcuatc, nearly central 03. 



..-, j Valve broad. R. 0,oL' mm C. Triangulum Ehb. 



"' \ — narrow. B. less than 0,oi mm C. hebridica Greg. 



Central area not dilated in the middle C. actifiuscula Cl. 



— abruptly dilated into a central area G4. 



. . j Large. L. 0.05 to O.i mm 65. 



63. {^'^ 



\ Small. L. 0,o.s to 0,04 mm 66. 



„^ I Striae about 10 in 0,oi mm C. acuta A. S. 



' \ — — 17 — — C. oregonica Cl. 



„„ j Central area rounded C. lapponica Grun. 



I — — dilated outwards C. .sfanroveiformis Lagst. 



1. C. microcepliala Grun. (18S0). — V. almo.st symmetrical, linear, with rostrate-capitate 

 end.s. L. 0,0 15 to 0,o2.s; B. (),oo3 to 0,iio4 mm. Median line almost central, straight; its central 

 pores approximate. Axial and central areas indistinct. Strife 24 to 30 in 0,01 mm. almost pa- 

 rallel. — Gritn. in V. H. Syn. p. ()3 PI. VIII f. 3fi to 39. C. mhviscula A. S. Atl. IX f. 08 to (U? 



Fresh water: Greenland! Scotland! Sweden (Vernamo, fossil)! Belgium (V. H.), Ectiador, Banos! 



2. C. (EncyOiiemsi) (Jesatii Rabh. (isr)3). — V. nearly symmetrical, narrow lanceolate, 

 gradually tapering from the middle to the acute ends. L. 0,045 to 0,0-); B. 0,oo6 to 0,007 mm. 

 Median line almost central, with approximate central pores and slightly curved terminal fissures 

 at some distance from the ends. Axial area narrow; central area small. Striai radiate tin'oughout, 

 about 19 in 0,oi mm., very finely punctate. — Nar. cqypendiculata Grun. Verh. ISfiO p. 552 PL IV 

 f. 2i». Nar. Cesatii Rabh. Siissw. D. p. 39 PI. VI f. 89. V. H. Syn. p. 88 PI. VIII f. 35. Cym- 

 hclla Crsatii Grun. A. S. Atl. LXXI f. 48, 49. 



Fresh water: Greenland! Iceland! Swedish and Russian Lappland! Scotland! Sweden (We- 

 uei'u)! Belgium (V. H.), Piedmont (Rabh.), Canada! 



This form, easily recognized l)y the distance of its terminal nodules from the ends of the 

 valve, is so slightly asymmetrical, that one might regard it as a Navieula. It seems to be an in- 

 liabitant ])rincipally of northern or alpine regions. In Verh. 18()0 (p. 571 PI. A^'II f. l(i) Grunow 

 mentions a (Jollrfonema chihinm as occurring together with C. Cesatii (his Nar. apprniliculata) and 



