HuTTON. — On a new Genus of Eissoinae. 147 



Art. XVII. — On a new Genus of EissoinaB. By Professor F. W. Hutton. 



[Read before the Philosophical Institute of Canterbury, 3rd November, 1881.] 



Plate I. 



There is a small mollusc, common in the rock pools in Lyttelton Harbour, 

 that I cannot bring into any genus in Adams' " Genera of Eecent 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 geniis 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. 

 Dardania. Gen. nov. 



Animal. Foot large, rounded in front, and emarginate behind ; opercu- 

 lar lobe small, simple. Kostrum emarginate at the extremity ; tentacles 

 long, and setaceous ; eyes large, on swellings at the outer bases of the 

 tentacles. Operculum ovate, sub-spu'al, with a long shelly process from 

 below the nucleus. Shell ovate, sub -conical ; whorls smooth ; apertm*e 

 oval, entire, rounded in front, peritreme not continuous, outer lip thm ; 

 axis imperforate. 



D. OLivACEA. 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 I., FIG. K. 

 K Dardania olivacea, x 10 times. 



2. „ ,, animal x 10 times. 



3. „ „ teeth x 470 times. 



4. „ ,, operculum, inside, x 30 times. 



