16 
NILS ODHNER, NORTHERN AND ARCTIC INVERTEBRATES. V. PROSOBRANCHIA. 1 DIOTOCARDIA. 
B. Lateral teeth of the radula 4 on each side; whorls slightly convex with 3— 
4 spiral ribs of uniform strength; colour pearl-white; animal differing from 
all Trochide by 4 lateral cirri on each side (instead of 3). H. 10—14 mm 
C. occidentale (MIGHELS & ADAMS 1841). 
Pl. 3 figs. 24—25. 
Craspedotus PHiriePi 1847. 
Danilia BRUSINA 1865. 
Shell elevated, imperforate; spiral cords 3—4 on the upper, 9 on the last whorl. H. 7—8, D. 6—7 
mm (France, LocARpD 1892) C. otavianus (CANTRAINE 1835) 
I 
(= Monodonta Tinei CALcARaA 1839). 
Margarita LEAcH 1819. 
Radula with a rudimentary lateral tooth; lamell&e denticulated in the inner and 
the outer margin. 
A. Shell smooth, without sculpture (except extremely fine spiral lines on the 
base), depressed conical; umbilicus narrow, not surrounded by a carina; 
aperture twice the spire in height; colour grayish green or reddish brown; 
radula &.1.(6.1.6).1. 0, the central cusp of the median tooth < their 
lateral denticles; height of the last whorl above the columella, seen from 
aperture, = half its breadth. H. circa 4—9; D. cirea 5—11 mm 
M. helicina PHiPePs 1774. 
PI. 3 figs. 26- 34; PING6Ifes. 3-5. 
B. Shell with spiral sculpture (sometimes absent in M. groenlandica). 
1. Sculpture consisting of very fine and dense spiral strige; umbilicus 
narrow; colour light yellowish or greenish, sometimes dark bluish, often 
vividly iridescent. Spire usually elevated, longitudinal sculpture (lines 
of growth) feebler than the spiral one; shell shining. Radula 0.1. 
(5.1.5).1. 0. H. 6—10, D. 6—11 mm MM. olivacea (BROwN 1827) 
(= M. argentata GouLrp 1841). 
Pl. 3 figs. 41—46; Pl. 4 figs. 1—3; Pl. 6 figs. 8—10. 
Spire usually more depressed; longitudinal sculpture of very fine 
dense-set lamellxe of about the same strength as the spiral lines, 
which are fainter than in the type; shell of a light colour, not 
shining; radula 0. 1.(4.1.4).1. o& var. gigantea LECHE 1878. 
Pl. 3 fig. 44: Pl. 4 fgs: 2—3; PII6ERoStobisS Ao: 
Sculpture consisting of coarse and sparse ridges or of sparse impressed 
lines (sometimes absent); umbilicus usually wide; shell often not irides- 
cent. 
a. No prominent longitudinal sculpture, though irregular strige or folds 
sometimes are present at the suture; spiral ribs or strie mostly 
present, seldom wanting; usually no keel around the umbilicus: 
height of the last whorl, above the columella, seen from aperture, 
Da 
