20 NILS ODHNER, NORTHERN AND ARCTIC INVERTEBRATES. V. PROSOBRANCHIA. 1 DIOTOCARDIA. 
b. Spire higher, shell more depressed; aperture < half the breadth of 
the shell. bh 
+. Surface sculptured all over by spiral strie; oblique spire height 2/5 of the aper- 
ture; umbilicus wide; colour white. H. 1, D. 1.3 mm; Wh. 3 
C. Willei FrieELE 1886. 
++. Only the base striated. 
2. Shell moderately depressed, its height nearly as large as 
the breadth, umbilicus moderately wide or narrow, not 
perspective. 
X. Aperture slightly angulated above; oblique spire height ?/1+ of the 
aperture; whole surface microscopically rugulated; base with numerous 
strige; colour yellowish white. H. 1.1, D. 1.3 mm; Wh. 3 
C. rugulosum (JEFFREYS M. 8.) G. 0. Sars 1878. 
XX. Aperture circular; oblique spire height '/s of the 
aperture; surface smooth, but the apical whorls with 
1—2 spiral lire and the base with more or less con- 
spicuous strig; colour grayish. H. 1.6; D. 1.38 mm; 
Wh. 4 C. turgidum n. sp. 
P1. 5" fig. SOCKET ShSAT. 
p. Shell highly depressed, its height about ?/3s of its breadth; umbilicus wide, 
perspective; base with numerous strixe; aperture slightly angular above; colour 
transparent white, sometimes yellowish. H. 1.2, D. 1.8 mm; Wh. 3—24 (Eng- 
land) C. serpuloide (MontAGuU 1808) 
(= Skenea? divisa ForBEs & HAnLEY 1853). 
2. Basal strie 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 strie; colour opaque white. H. 1.3, D. 2 mm; Wh. 4 
C. trochoide (JEFFREYS M. S.) G. O. SaArRs 1878. 
Shell narrowly umbilicated, wholly smooth 
var. Peterseni FRIELE 1877. 
Pl. 5 fig. 41. 
b. Shell depressed; oblique spire height ”/s of the aperture; umbilicus 
wide; basal strie distinct; colour white. H. 1.2, D. 1.838 mm; Wh. 3 
C. levigatum (JEFFREYS M. S.) G. O. SaArs 1878. 
Fam. Adeorbidea. 
I. Shell depressed, thin, with flattened base, obviously spirally sculptured; aperture oblique 
Adeorbis S. Woop 1842. 
II. Shell globular, thin, nearly smooth or microscopically reticulated; aperture roundish 
Archytea Costa 1869 
(= Trachysma [JErFreys M. S.] G. 0. Sars 1878). 
