* 
Hutrron.—On a new Genus of Rissoine. 147 
Art. XVII.—On a new Genus of Rissoine. By Professor F. W. Hurron. 
[ Read before the Philosophical Institute of Canterbury, 3rd November, 1881.) 
Plate I. 
Tuer is a small mollusc, common in the rock pools in Lyttelton Harbour, 
that I cannot bring into any genus in Adams’ ‘‘ Genera of Recent Mollusca.” 
The shell is like that of Barleeia, but the operculum is sub-spiral, like that 
of Rissoina, but without the marginal ridge. The animal differs from 
Rissoina in having the opercular lobe simple, and the foot emarginate 
behind, as in Barleeia, but from this genus it differs in having the tentacles 
long and setaceous, and the rostrum emarginate. From all other genera it 
is distinguished by the process on the operculum. 
Darpania. Gen. nov. 
Animal. Foot large, rounded in front, and emarginate behind ; opercu- 
lar lobe small, simple. Rostrum emarginate at the extremity; tentacles 
long, and setaceous ; eyes large, on swellings at the outer bases of the 
tentacles. Operculum ovate, sub-spiral, with a long shelly process from 
below the nucleus, Shell ovate, sub-conical ; whorls smooth; aperture 
oval, entire, rounded in front, peritreme not continuous, outer lip thin; 
axis imperforate. 
D. ontvacea. Sp. nov. 
: Plate I., fig. K. 
Shell small, ovate, olive brown when alive, purplish black when dry ; 
Whorls four, convex, smooth, with fine lines of growth. Length -08: 
breadth -06. 
Animal light brown, foot and tentacles white. The sole of the foot 
has a median longitudinal groove, and the tentacles are smooth. The 
central tooth is as broad as long, and with two denticles on each side of the 
median denticle. The first lateral tooth has five denticles, the middle one 
larger than the others. The second lateral has three denticles, the inner 
One the smallest. The third lateral is narrow, abruptly bent and expanded 
near the base, it has three minute denticles. 
Habitat: On seaweed in rock pools ; Lyttelton Harbour. 
It is probable that some of the New Zealand species described as Rissoina, 
or Barleeia, may. belong to this genus, as in none of them is the animal or 
the operculum known. 
EXPLANATION OF PLATE L., FIG. K. 
K Dardania olivacea, x 10 times. 
id ” és animal x 10 times. 
” ” teeth x 470 times, 
” » operculum, inside, x 30 times. 
