ODOSTOMIA. 299 



O. SPIRALIS, Montagu. 



Bluntly conic; lower half of the body-whorl spirally ribbed ; 

 elsewhere longitudinally ribbed ; fold small but distinct. 



Plate XCVII. fig. 2, and (Animal) Plate FF. fig. 8, 9. 



Turho spiralis, Mon't. Test. Brit. vol. ii. p. 323, pi. 12, f. 9. — Turt. Conch. 



Diet. p. 222. 

 Voliita „ Maton and Rack. Trans. Linn. See. vol. viii. p. 1 30. 



" pellucidu, DiLLW. Recent Shells, vol. i. p. 508. — Wood, Index Testae, 

 pi. 19, f. 23. 

 Odostomia spiralis, Fleming, Brit. Animals, p. 310. — Alder, Ann. Nat. Hist, 

 vol. xiii. pi. 8, f. 13, animal (imperfect). — Johnston, 

 Berwick. Club, vol. i. p. 273.— Macgilliv. Moll. Aberd. 

 p. 155.— Brit. Marine Conch, p. 172.— Alder, Cat. Moll. 

 Northumb. and Durh. p. 52, animal. — Jeffreys, Ann. 

 Nat. Hist., nevir ser. vol. ii. p. 342. 

 „ plicalula, Macgilliv. Moll. Aberd. p. 154, (Young, fide Jeffreys, 

 from type ; copied as Jaminia plicatula. Brown, 111. 

 Conch. G. B., p. 129). 

 Rissoa spiralis. Brown, Illust. Conch. G. B., p. 13. 



The peculiarity of the sculpture of this shell renders 

 it the most easily recognizable of our British Odostomia:. 

 It ranges in shape from ovate-conic to oblong-conic, is 

 tolerably strong, consequently not very transparent, though 

 a little translucent, and of an uniform more or less glossy 

 white. Numerous straight square-cut and closely disposed 

 ribs traverse the whorls in a longitudinal direction, and 

 extend, except upon the body, on whose lower half they 

 are replaced by rather depressed and broadish spiral ribs, 

 from top to bottom. Above the broad and canalicu- 

 lated suture, which runs rather obliquely, they are apt to 

 become abruptly confluent so as to form an obscure spiral 

 costella, but this character is not always perceptible. The 

 five whorls are more or less flattened and simple ; they are 

 of slow longitudinal increase, and taper moderately : the 



