KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 26. N:0 2. 



49 



38. 



39. 

 40. 

 41. 

 42. 

 43. 

 44. 

 45. 

 46. 

 47. 

 48. 

 49. 

 50. 

 51. 

 52. 

 53. 



54. 



55. 

 56. 

 57. 

 58. 

 59. 

 60. 

 61. 

 62. 

 63. 

 64. 



Axial and central areas indistinct 



— area narrow, central area distinct 



— and central areas united to a lanceolate space 

 f StrisB 12 to 13 in 0,oi mm. . . . 

 I — 20 to 21 — . . . . 



{Central area large 

 — — small 



I Elliptical, obtuse . ... 



\ Lanceolate, acute 



{Terminal fissures in contrary directions . . . 

 — — tliB same 



J L. 0,025 mm. . . . 



\ L. 0,05 mm. . .... . . . . 



f Longitudinal lines marginal or inframarginal . 

 I — — median . . .... 



j Breadth 0,009 mm. 



\ — 0,02 to 0,03 mm. ... 



j Longitudinal lines single . . . 



\ — — double or triple 



f Striae 9 to 10 in 0,0l mm 



\ - 12 - - 



f Longitudinal double-lines approximate . 



\ — — distant _ . . 



/ Striae very fine, 28 in 0,oi mm. . . ... 



1 — distinct 



j Central area with longitudinal marks or rows of puncta 

 I — — without — — — 



I Axial area narrow, central area rounded 



\ — and central areas united to a linear or lanceolate 



{Yalve with broad ends 

 — narrowed towards the ends 



fL. 0,05 to 0,06 mm . . ... 



\L. 0,108 mm . ... 



Strise 7 or 8 in 0,oi mm. . . . . . . 



— 10 to 12 — .... .... 



— 20 — — . 



(Longitudinal lines fine . . .... . . 

 — — broad 



I Axial area indistinct . .... 



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

 j Central area small or indistinct . . 



I — — orbicular . . . . 



( Striae 8 to 10 in 0,oi mm. . . . .... 



t — 11 to 20 — 



j Longitudinal lines double ... 



I — — single . . . . . . 



{Striae parallel . . . .... .... 



— slightly radiate . . . . . . . . . 



{Valve gibbous in the middle and at the ends . . . . . 



— with parallel margins . . . ....... 



j Freshwater species .... . . . . . 



1 Marine — 



f Longitudinal lines median . . • ■ . . . 



\ — — marginal . . 



/ Longitudinal lines median . . . . 



\ — — inframarginal .... 



space . 



. 39. 



40. 



44. 



. . C. tahitensis Geun. 

 . . C. virginea Cl. 



41. 



42. 



C. brevis Geeg. 



. . C. Duseni Cl. 



. C. ahnormis Grun. 



43. 



C ladogensis Cl. 

 . . C. Holstii Cl. 



45. 



46. 

 C Lagerheimii Cl. 

 C. latiuscula Kutz. 

 C. amphishoena Boey. 



47. 



. . .48. 

 C. hivittata Pant. 

 . . C. permagna Bail. 

 0. madagasearensis Cl. 

 . C. lepidula Getjn. 

 . . . 50. 

 .... 51. 

 ... .55. 



. C. Liber var. 

 52. 

 . . 53. 



54. 



. C. obtusa W. Sm. 



. . . C. Kainitzii Pant. 



. . . C. sectilis A. S. 



. . C. samoensis Geun. 



. . C. alpestris Geun. 



56. 



65. 



57. 



.... 64. 



58. 



. C. Anderssoni Cl. 



59. 



61. 



C. probabilis A. S. 



60. 



C. robusta Geun. 



C. Eugenics Cl. 



C. Silicula Ehb. 



62. 



C. bacillaris Geeg. 



63. ') 



C. Liber W. Sm. 



C. Spathula Bbun. 



C. formosa Greg. 



. C. Frater Cl, 



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

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



