GASTEROPODA. 117 



3. C^CUM GLABRUM. Mont. Tab. XX, fig. 6. 



DENTALIUM GLABRUM. Mont. Test. Brit. p. 497. 1803. 



CAECUM GLABKUM. Flem. Ediu. Ency. vii, p. 67, t. 204, fig. 7, 1817. 



ORTHOCERA GLABRA. Flem. Brit. An. p. 237, 1828. 



DENTALIUM GLABRUM. Turt. Conch. Diet. p. 40, 1819. 



BROCHUS GLABRUS. Brown. Illust. Brit. Conch, pi. 1, fig. 3, 1827. 



L/EVIS. p l. 1, fig. 6. 



C^CUM GLABRUM. S. Wood. Catalogue 1842. 



DENTALIUM GLABRUM. Thorpe. Brit. Mar. Conch, p. 4, fig. 5, 1844. 



DENTALIOPSIS GLABRA. Clark. MS. 1847. 



C. Testa pusilld, cylindricd, arcuatd, Icevigatd, politd; antice simplici, non marginatd ; 

 postice dausd, obtusd, convexd, submarginatd. 



Shell very small, cylindrical, curved, smooth, and glossy ; anterior extremity simple, 

 not marginated or thickened ; posterior termination, with an obtuse convex clausum, 

 submarginated. 



Length^ ^ of an inch. 



Locality. Cor. Crag, Sutton. Recent, Britain. 



I have only two specimens of this shell, they, however, are so precisely similar to 

 the recent species, that I have no hesitation in considering them identical. They are 

 perfectly smooth, smaller than any of my specimens of C. mammillatum, and they are 

 more particularly distinguished by having the posterior termination closed by a 

 perfectly convex clausum, marginated by the edge of the shell. 



4. C^CUM (?) INCURVATUM (?). Walker. Tab. XX, fig. 7, a b. 

 SERPULA INCURVATA. Walker. Test. Min. Rar. fig. 11, 1787. 

 VERMICULUM INCURVATUM. Mont. Test. Brit. p. 518, 1803. 

 SERPULA INCURVATA. Turt. Conch. Diet. p. 156, 1819. 

 CORNUOIDES MAJOR. Brown. Illust. Brit. Conch, pl. 1, fig. 49, 1827. 

 SERPULA (?) RECTA. S. Wood. Catalogue 1842. 



C. Testa minima, l&vigatd, politd, tenui, fragili ; antice cylindraced, apertd, non mar- 

 ginatd ; postice incurvd, convolutd. 



Shell very minute, smooth, glossy, thin, and fragile; anterior portion cylindrical, with 

 a simple but not marginated aperture ; posterior portion incurved, with two volutions. 



Length, nearly ^ a line. 



Locality. Cor. Crag, Sutton. ? Recent, Britain. 



Three specimens of this minute shell, found by myself in the sand of the Coralline 

 Crag, appear to resemble the figures given of the recent species. 



Mr. Jeffreys informs me that he believes this to be only the young or immature 

 state of Ccecum glabrum, and that decollation takes place at a certain period of its 

 existence when the posterior termination is differently closed. Until further observa- 

 tions shall have confirmed the correctness of this opinion, it may be as well to allow 

 it to remain as a distinct species, in proximity with what are, no doubt, its true 

 relations. 



