20 NILS ODHNER, KORTHERN AND ARCTIC INVERTEBRATES. V. PROSOBRANCHIA. 1 DIOTOCARDIA. 



b. Spire higher, shell more depressed ; aperture < half the breadth of 

 the shell. 



+ . Surface sculiitured all over by spiral stria' ; oblique spire height ^/d of the aper- 

 ture; iiuibilicus wide; colour white. II. 1, 1). \.ö mm; Wh. 3 



C. Willei FßiELE 1886. 



+ + . Only the base striated. 



a. Shell moderately depressed, its height nearly as large as 

 the breadth, umbilicus moderately wide or narrow, not 

 perspective. 



X. Aperture slightly augulated above; oblique spire height ''/i of the 

 aperture; whole surface microscopically rugulated; base with numerous 

 strife; colour yellowish white. H. l.i, D. 1.3 mm; Wh. 3 



C. rugulosum (Jeffreys M. S.) G. 0. Saes 1878. 

 X X . Aperture circular ; oblique spire height */5 of the 

 aperture; surface smooth, but the apical whorls with 

 1 — 2 spiral lira? and the base with more or less con- 

 spicuous strise; colour grayish. H. 1.6; D. 1.8 mm; 

 Wh. 4 C. turgidum n. sp. 



PI. 5 %. 39; PI. 7 fig. 7. 



ß. Shell highly depressed, its height about '^/n of its breadth; umbilicus wide, 

 perspective; base with numerous striae; aperture slightly angular above; colour 

 transparent white, sometimes yellowish. II. 1.2, D. 1.8 mm; Wh. 3 — 4 (Eng- 

 land) C. serpuloide (Montagu 1808) 



(= Skenea? divisa Forbes & Hanley 1853). 

 Basal stria? absent or arcuated, with their foremost ends bent down 

 into the umbilicus. 



a. Shell globose; oblique spire height about of the aperture; um- 

 bilicus a narrow fissure or wholly covered; base with nearly in- 

 conspicuous strise; colour opaque white. H. 1.8, D. 2 mm; Wh. 4 



C. trochoide (Jeffreys M. S.) G. 0. Sars 1878. 

 Shell narrowly umbilicated, wholly smooth 



var. Peterseni Friele 1877. 



PI. .5 fig. 41. 



b. Shell depressed; oblique spire height ^/s of the aperture; umbilicus 

 wide; basal stria? distinct; colour white. H. 1.2, D. 1.8 mm; Wh. 3 



C. Isevigatum (Jeffreys M. S.) G. 0. Sars 1878. 



Fam. Adeorbidae. 



I. Shell depressed, thin, with flattened base, obviously spirally sculptured; aperture oblique 



Adeorbis S. Wood 1842. 



II. Shell globular, tliin, nearly smooth or microscopically reticulated; aperture roundish 



Archytfea Costa 1869 

 {-■= Trachysma [Jeffreys M. S.] G. 0. Sars 1878). 



