18 
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NILS ODHNER, NORTHERN AND ARCTIC INVERTEBRATES. V. PROSOBRANCHIA. 1 DIOTOCARDIA. 
Sculpture consisting of longitudinal folds and very fine spiral strie, more dis- 
tinet on the base; 1—3 umbilical keels present; shell conical, whitish, greenish 
or” brownish. -H. 8—11; D:-9—12 mm. Radula 11—12.:1.(3:1.3). 1:11—12 
S. varicosa (MIGHELS & ADAMS 1842) 
(= Margarita elegantissima S. Woop 1848). 
Pl. 5 figs. 6—14; PI. 7 figs. 5—6. 
Sculpture consisting of spiral keels, which are usually more prominent than 
the longitudinal folds or strie; colour whitish, greenish or brownish. Radula 
5—-10.1.(2.1.2).1.5—10. Type with 1—2 prominent spiral ridges and fine 
strige; umbilical keel present. H. circa 7, D. 8 mm 
S. obscura (CouTHouYy 1839). 
Pliö fis: 225 PlITetesrN0 
(Specimens with 3 strong spiral ridges and a feeble umbilical keel pass over 
into var. finmarchica.) 
a. Spiral ridges many, strong, though 2—3 are more prominent than the rest; 
umbilical keel present var. cinergeformis LECHE 1878. 
b. Spiral ridges many, of about uniform strength; umbilical keel present 
var. albula GouLD 1862. 
Pl. 5 fig. 20. 
(Specimens without umbilical keel pass over into var. bella.) 
c. Spiral ridges replaced by fine and dense strie; umbilical keel present 
var. intermedia LECHE 1878. 
PErSrgeN3: 
d. Spiral ridges 4—5, unequal in strength; fine longitudinal strig; no umbi- 
lical keel; H. 4.5; D. 5 mm var. finmarchica n. n. 
(= Macheroplax obscura CouTtH. of SARS 1878). 
Pl. 5 figs. 36—35. 
e. Spiral ridges about 7, unequal in strength; longitudinal strie indistinct; 
no umbilical keel; H. 4.8; D. 6.4 mm var. multilirata n. var. 
Pl. 5 figs. 28—30. 
f. Spiral lire undeveloped, replaced by finer strixe, about 6—8 on the last 
whorl; no umbilical keel. H. 4.5, D. 5.8 mm «var. islandica OÖDHNER 1910. 
RITA: 
g. Longitudinal sculpture coarse and distant, often of nearly the same strength 
as the spiral one; this consisting of a few equally strong ridges; umbilical 
keel present or not. Radula with 5—98 lamell&e on each side. H. 6.5, D. 
7 mm var. bella (VERKRUZEN 1875) G. O. SaArs 1878. 
P1. 5 figs. 25—27, 31, 34. 
Sculpture consisting of spiral riblets and rows of tubercles (surface of the shell 
nodulous or granular). 
A. 3 prominent spiral ridges on the last whorl and 1 on the base, surrounding 
the umbilicus; aperture roundish; colour pearl-white. H. 8, D. 7 mm. 
Radula 5. 1.(3- 1:53): 1:35 (ERIELE 1877) S. cincta (PHILIPPI 1836) 
(= Trochus amabilis JEFFREYS 1865). 
