ODOSTOMIA. 303 



perforation, but only a slight umbilical crevice. The length 

 of the shell is not quite a line, and the breadth is from one- 

 third to one-fourth less. 



The animal has not been observed. 



The species is of extreme rarity, and has only been ob- 

 tained chiefly, if not entirely, from shell-sand at Scar- 

 borough, Sandwich, Exmouth, Burrow Island, Swansea, 

 Tenby, and the west coast of Scotland. (Jeff. Ann. Nat. 

 Hist.), 



O. DEcussATA, Montagu. 



With numerous raised spiral lines in the intervals of the longi- 

 tudinal ribs : whorls more or less rounded, of quick longitudinal 

 increase : fold obsolete. 



Plate XCVII. fig. G, 7. 



Turbo pellucidus, Adams, Trans. Linn. Soc. vol. iii. pi. 13, f. 33, 34 ? 



„ decussatus, Mont. Test. Brit. p. 322, pi. 12, f. 4. — Turt. Conch. Diction. 



p. 210. — Fleming, Brit. Animals, p. 299.— Brit. Marine 



Conch, p. 169. 

 Helix arenaria, Maton and Rack. Trans. Lin. Soc. vol. viii. p. 214. 

 Turbo arenarius, (not of Turton) Dillw. Recent Shells, vol. ii. p. 839. — Wood, 



Index Testae, pi. 31, f. 54. 

 Rissoa arenaria, BROwn, Illust. Conch. G. B., p. 12, pi. 9, f. 12. 

 Odostomia pellucida, Jeffreys, Ann. Nat. Hist, new series, vol. ii. p. 344. 



The identity of this species with the T. pellucidus of 

 Adams is too conjectural to hazard a substitution of his 

 name for the more appropriate one bestowed by Montagu. 

 The shell has a narrow oblong shape, and tapers to an 

 obliquely set and bluntish apex ; it is moderately strong, 

 not very transparent, a little glossy, and of an uniform 

 white. The principal or lower volutions are adorned with 

 very numerous longitudinal pliciform riblets, that are closely 

 decussated throughout by elevated spiral lines ; the former, 

 which extend from the top to the bottom of each whorl, 



