176 MOLLUSCA FROM THE CRAG. 



this shell is spoken of as perfectly smooth ; but their examination must have been of 

 ill-preserved individuals, the striae being very minute and little impressed, they are 

 easily obliterated. 



A specimen from the Mammaliferous Crag, near Norwich (fig. 1 ), was found by 

 Mr. Wigham ; it has a diameter greater than three fifths of its axis, with a curved or 

 semicircular outer lip, and is, I imagine, only a variety of this species. 



5. BULLA CONCINNA. S. Wood. Tab. XXI, fig. 6, a c. 



BULLA CONCINNA. S. Wood. Illust. in Mag. Nat. Hist. 1839. p. 463, pi. 7, fig. 7. 

 S. Wood. Catalogue 1842. 



B. Testa minutd, subcylindraced, tenui, f raff Hi ; transversim tenuissime, striatd, et 

 longitudinaliter decussatd ; vertice umbilicato ; spird inclusd ; columella obsolete uniplicatd. 



Shell small, subcylindrical, thin, and fragile, finely striated transversely, and 

 decussated by the lines of growth; vertex umbilicated ; spire hidden; inner lip slightly 

 replicate, with an obsolete fold upon the columella. 



Axis, I of an inch ; diameter, of its length. 



Locality. Cor. Crag, Sutton. 



Unfortunately, since the publication of the description of this species at the 

 above references, I have not found a specimen larger or more perfect than what I 

 then possessed. It is very probable that this may be the young of Sulla clathrata, 

 Defrance, B. Tarbelliana, Grateloup, Bord, foss. p. 58, f. 29-30. The principal 

 difference appears to be in the size, although, from the figures, our shell is rather less 

 cylindrical, with an obtuse fold upon the columella, which is most visible in broken 

 specimens. I have left it with my own name for the present, until some better 

 specimens are found to confirm either the one or the other. 



6. BULLA TRUNCATA. Adams. Tab. XXI, fig. 3, a c. 



BULLA TRUNCATA. Adams. Linn. Trans. V, t. 1, fig. 1-2, 1797. 

 Mont. Test. Brit. p. 223, t. 7, fig. 5, 1803. 



RETUSA. Maton and Rack. Linn. Trans, vol. viii, 1807. 

 VOLVARIA RETUSA. Srown, Illust. Brit. Conch, pi. 38, fig. 17-18, 1827. 

 BULLA TRUNCATA. Flem. Brit. Animals, p. 293, 1828. 



SEMISULCATA. Phil. En. Moll. Sic. vol. i, p. 123, t. 7, fig. 9, 1836. 

 SUBTRUNCATA. S. Wood. Illust. Mag. Nat. Hist. pi. 7, fig. 9, 1839. 

 TRUNCATA. Phil. En. Moll. Sic. vol. ii, p. 96, 1844. 



S. Wood. Catalogue 1842. 

 CYLICHNA TRUNCATA. Loven. Ind. Moll. Scand. p. 10, 1846. 



B. Testa pusilld, cylindricd, Icevigatd; basi vios dilatatd ; aperturd sup erne anguste 

 lineari ; in/erne paululum latiore ; vertice truncato, vel late umbilicato ; spird distinctd, 

 plied ad basim columella parum manifestd. 



Shell minute, cylindrical, and smooth, with a little contraction in the middle, or 



