98 Mr. Thompson on the Mollusca of Ireland. 



fully studied our native Mollusca before his attention was 

 directed to botany, in which department his labours have now 

 long been known and appreciated. 



Rissoa tristriata, mihi. PI. II. fig. 10. 



R. conic, volutions 5|, rounded, smooth, with spiral rows of 

 tawny spots, first whorl very large, aperture roundish oval, umbi- 

 licus none, 3 striae winding round the summit of each whorl. 



Length 1^ line. 



A connecting link between R. semistriata and R. interrupta. 



Found at Youghal by Miss M. Ball. 



Rissoa Ballice, mihi. PI. II. fig. 9. 



R. elongated, white, apex obtuse, 5 slightly rounded whorls, 

 deeply marked longitudinally with somewhat distant striae, aperture 

 ovate, margin of the mouth thin, lower portion of the first whorl 

 spirally striated. Length 1 j line. 



Although of a more slender form, this species, in sculpture, 

 &c., somewhat resembles Odostomia spiralis, but is a true 

 Rissoa. 



Found at Youghal by Miss M. Ball, after whom it is 

 named, though a very trivial compliment to her acquirements 

 in different departments of the Invertebrata of Ireland. 



^ Turritella fulvocincta, mihi. 



T. with about 1 1 whorls, transversely ribbed, spirally striated, 

 whitish, with a single fulvous band winding round the volutions. 



Length 3 J lines. 



Found at Portmarnock, near Dublin; and communicated to 

 me by Miss M. Ball. 



^^ Cerithium reticulatum, var. /3.^^ Harvey's MS. PL II. 



fig. 8. 



Whorls 9 or 10, with three spiral ridges, the uppermost very pro- 

 minent and forming a keel round the suture, ridges crossed by some- 

 what distant longitudinal furrows. 



Length 3^ lines, breadth 1^ ; colour purplish brown. 



This shell differs from C. reticulatum in the prominent 

 keel bounding the whorls on the upper side, and in the spiral 

 furrows being much deeper than the longitudinal, and these 

 rather less marked than in that species. 



