KONGL. SV. VET. AKADEMIENS HANDUNGAR. BAND 26. N:0 2. 49 



i Axial and central areas indistinct 39. 



38. ■! — area narrow, central area distinct 40. 



I — and central areas united to a lanceolate space 44. 



39. 

 40. 



41. 

 42. 

 43. 

 44. 

 45. 

 46. 

 47. 

 48. 

 49. 

 50. 

 51. 

 52. 

 53. 



55 

 56 

 57, 

 58. 

 59. 

 60. 

 Gl. 

 62. 

 63. 

 64. 



Striffi 12 to 13 in 0,oi mm C. tahitensis Grun. 



20 to 21 — C. virginea Cl. 



Central area large 41. 



— small 42. 



/ Elliptical, obtnse C. brevis Geeö. 



I Lanceolate, acute C. Diiseni Cl. 



I Terminal fissures in contrary directions C. abnormis Grun. 



\ — — tlie same — 43. 



) L. 0,025 mm C. ladogensis Cl. 



\ L. 0,05 mm C. Holstii Cl. 



) Longitudinal lines marginal or inframarginal 45. 



I -^ — median 46. 



J Breadth 0,oo9 mm C. Lagerheimii Cl. 



\ — 0,02 to 0,03 mm C. latiuscida KtJTZ. 



J Longitudinal lines single C. amphisboena Bory. 



I — — double or triple 47. 



( Stris! 9 to 10 in 0,oi mm 48. 



1—12 ~ — C. bivittata Pant. 



j Longitndinal double-lines approxiraate • C. permagna Bail. 



1 — — distant C. madagascarensis Cl. 



) Striae very fine, 28 in 0,oi mm C. lepidula Grun. 



1 — distinct -..,50. 



Central area wifh longitudinal marks or rows of puncta 51. 



— witliout — — — 55. 



1 



( Axial area narrow. central area rounded C. Liber var. 



I — and central areas united to a linear or lanceolate space 52. 



I Valve with broad ends 53. 



I — narrowed towards the ends 54. 



jjj. 0,05 to 0,06 mm. . . • C. obtusa W. Sm. 



\L. 0,108 mm ' C. Kainitzii Pant. 



[ StriEB 7 or 8 in 0,oi mm C. sectilis A. S. 



54. < — 10 to 12 — C. samoensis Grun. 



I — 20 — — C. alpestris Grun. 



i Longitudinal lines fine 56. 



I — — broad 65. 



j Axial area indistinct 57. 



\ Axial and central areas united in a linear or lanceolate space 64. 



J Cenlral area small or indistinct 58. 



1 — — orbicular C. Anderssoni Cl. 



1 Striae 8 to 10 in 0,01 mm 59. 



1 — 11 to 20 — 61. 



J Longitudinal lines double C. probabilis A. S. 



1 — — single 60. 



J Striae parallel C. robusta Grun. 



\ — slightly radiate C. Eugenim Cl. 



I Valve gibbous in tbe middle and at tlie ends C. Silicula Ehb. 



I — witli parallel margins 62. 



J Freshwater species C. bacillaris Greg. 



1 Marine — 63. •) 



j Longitndinal lines median C. Liber "W. Sm. 



\ — — marginal C. Spathula Brun. 



( Longitudinal lines median C. formosa Greg. 



( — — inframarginal C. Fräter Cl. 



') In this division C? elongatula Pant. may probably alsn be included. 

 K. Vet. Akad. Handl. Band 26. N:o 2. 



