174 



{ 



12. 



Median line sigmoid 10. 



straight • 13. 



., j Valve with an annulns at the side of the centre C. cyclophora Gedn. 



\ — without 11. 



.... J Striae of the upper valve coarse (9 to 11 in 0,oi mm.) 12. 



' \ — — — — fine (25 — — — ) C. heteroidea Hantsoh. 



I Central nodule transversely dilated C. arctica Cl. 



\ — — not — — C. voluta Br. 



..„ j Lateral areas connected to a broad marginal annulus 14. 



^"^- t - - not - - - - - 15. 



... j Strise of the upper valve composed of coarse puncta C. antiqua Br. 



' \ — — — — costate with a median punctum C. interrupta Grtjn. 



ir J Uppei' valve with longitudinal furrows or depressions 16. 



\ — — without 18. 



..^ J With several, strong furrows G. pellucida Hantsch. 



J With severi 



\ — — a lunate depression 17. 



y ( Striae fine (16 to 24 in 0,oi mm.) punctate C. pseiidomarginata Grbg. 



I — coarse (10 in 0,oi ram.) costate, with a median punctnm C. vitrea Brun. 



o I Lateral areas crossed by two oblique rows of puncta C. pfcecellens Pant. 



' \ — — not — — — — — — C. Letourneuri Cl. 



1. C. inolesta (Ktliz. 1844) Grun. (1881). — Outline elliptioal, with broad, rounded ends. 

 L. 0,017 to 0,019; B. 0,007 to 0,008 mm. Upper V. with narrow axial area. Strite more than 30 

 in 0,01 mm. finely punctate, puncta forming zig-zag-lines. Lower V. with straight median line, 

 not reaching to the ends. Central area very small. Strite. more than 30 in 0, 01 mm. punctate, puncta 

 forming fine, longitudinal striiE. — Bac. p. 71 PI. V f. 7, 11, 12. V. H. Syn. Pl. XXX f. 18, 19. 

 A. S. N. S. D. Pl. III f. 20? 



Marine: Venice (Klitz.). 



Var. crucifera (tRUN. (1881). — L. 0, 01 5 to 0,025; B. 0,oo8 to 0, 01 6 mm. Central area of 

 the lower valve dilated to a transverse fascia. — V. H. Syn. Pl. XXX f. 20, 23. U. diapJiana 

 W. Sm. b. D. p. 22 Pl. XXX f. 254 (partim) 1853. A. S. Atl. CXCIII, 48 to 51. 



Marine: England! Coasts of France! 



Var. amygclalina (Bréb.) (xRUN. (1881). — L. O, oss to 0,045; B. 0,oi3 to 0,02 mm. Upper 

 V. with about 20 strise in 0, 01 ram. Lower V. with slightly dilated central area and about 27 

 striee in 0,oi mm. - C. cUaphana W. Sm. B. D. 1 p. 22 Pl. XXX f. 254 (partim). C. amygdalina 

 Grun. in V. H. Syn. XXX f. 5. 35. 



Marine: French coast of the English Channel! 



2. C. flnmarchica Grun. (1880). — EUiptical. L. 0,012 to O.015; B. 0,0055 to 0,oo7 mm. 

 Upper V. with linear axial area. Strise 20 in 0,oi mm. slightly radiate. Lower V. with straight 

 median line, ending near the margin. Central area a fascia, not reaching to the margin. Strise 24 

 in 0,01 mm. slightly radiate. — A. D. p. 16 Pl. 1 f. 1. 



Marine: Arctic America! Finmark! 



3. C. septentrionalis Grun. (1884). — EUiptical. L. 0,022 to OjO.^^e; B. 0,012 to 0,o2.s mm 

 Upjjer V. with narrow axial area. StritB 8 in 0, 01 mm. almost parallel, punctate; puncta 14 in 

 0,01 mm., larger at the margin, not arrauged in longitudinal rows. Lower V. with straight 

 median line. Central area a narrow, transverse fascia. Strise radiate, O in 0, 01 mm. punctate; 

 puncta K) in 0,oi mm. — Franz Josefs Land L. p. 55 PI. I f. 2. 



Marine: Assistance Bay (Grun.). 



4. A. Calcar Cl. (1891). — Broadly elliptical. L. 0,012; B. O,ooii mm. Upper V. with 

 straight, narrow axial area. (Jentral area on one side of the nodule dilated into a spurlike pro- 

 jection, on the othcr bifid, forming au horseshoe-like marking. Lower V.(?) with straight median 



