l4 NILS ODHNER, NORTHERN AND ARCTIC INVERTEBRATES. VV. PROSOBRANCHIA. 1 DIOTOCARDIA. 
Fissurisepta SEGUENZA 1863. 
Shell oval, conic, depressed, but with an elevated apical part, the summit of which is taken up by the 
subcircular foramen; sculpture consisting of radiating alternately larger and smaller, closely tuberculate strie; 
colour opaque whitish. $&L. 2.9; Br. 2.3 mm F. granulosa JEFFREYS 1882 
(= F. papillosa JEFFREYS 1870, not SEGUEnNzaA 1863.) 
Emarginula LAMARCK 1801. 
I. Sculpture reticulated of coarse and sparse longitudinal cords, mostly intermixed 
with smaller ones, and concentric ribs of about the same strength; colour white. 
L. 9—16 mm E. fissura (LINNÉ 1758) 
(= E. reticulata SOWERBY 1813). 
Pl. 2 figs. 42—45. 
II. Sculpture consisting of broad longitudinal fascicles of riblets alternating with 
finer threads and crossed by fine and close concentric lirge; colour white. 
08 - N E. crassa SOWERBY 1813. 
Pl. 2 figs. 46—50, PI. 3. figs. 1—2. 
Propilidium ForBEs & HANLEY 1849. 
Shell oblong, depressed, with subcentral apex, sculptured by fine and close-set 
radiating strige, granulated by crossing concentric ones; apex distinctly twisted; colour 
whitish. L. 4.3 mm P. ancyloide (FORBES 1840). 
RINGS? for: 
Fam. Trochidee. 
Animal with frontal lobes; jaws present; radula often with more than 5 lateral 
teeth on each side (subfam. Gibbulin2). 
I. Aperture quadrangular (not rounded); columella dentated or sinuated at base; 
outer lip smooth; shell solid, usually variegated and strongly sculptured. 
A. Shell umbilicated, usually spirally ribbed, but without sharp keels at the 
suture; radula 0 .1.(5.1.5).1. &, the rhachian tooth with its basal plate 
broader than long Gibbula Risso 1826. 
B. Shell imperforated, smooth or spirally keeled or granular; often a sharp 
ridge at the suture; radula 0 .1.(4—5.1.4—5).1. 0, the rhachian tooth 
usually with a longer than broad basal plate Calliostoma SWAINSON 1840 
(= Zizyphinus GRAY 1840). 
I. Aperture rounded; columella with a strong tooth below; outer lip thickened and nodulous within; shell 
solid, uniformly brownish; whorls rounded, sculptured with spiral cords and longitudinal lamellae 
Craspedotus PHiurPi 1847 (= Danilia BrRusinA 1865). 
III. Aperture rounded; columella simple; shell usually thin, smooth or variously 
sculptured but always unicoloured. 
A. Radula with numerous (> 40) lamell&e with recurved apex, denticulated on 
both sides; the lateral tooth incomplete (without cusp); shell smooth or 
spirally sculptured Margarita LEAcH 1819, 
