GASTEROPODA. 117 



3. C^cuM GLABRUM. 3font. Tab. XX, fio-. 6. 



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



C/ECUM GLABRUM. 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. ... pi. 1, fig. c. 



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, ct/lindricd, arcuatd, IcBvigatd, politd; antice simplici, non marginatd ; 

 postice clansd, obfusd, convexd, suhmarginatd. 



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. mammiUafum, and they are 

 more particularly distinguished by having the posterior termination closed l)y a 

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



4. Cecum (?) incurvatum (?). WaR-er. Tab. XX, fig. 7, a — b. 



Serpula ixNCURVATA. JVaHier. Test. Min. Rar. fig. 11, 1787. 

 Vermiculum incurvatum. Mont. Test. Brit. p. 518, 1803. 

 Serpula incurtata. Turt. Conch. Diet. p. 156, 1819. 

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

 Serpula (?) recta. S. Wood. Catalogue 1842. 



C. Testd minimd, lavigatd, politd, tenui, fragili ; antice cglindraced, apertd, non viar- 

 ginatd ; postice incurvd, convolutd. 



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

 a simple but not marginated aperture ; posterior portion incurv^ed, wath 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 Caecum 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 w^ell to allow 

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

 relations. 



