280 PYRAMIDELLIDiE. 



O. xiTiDA, Alder. 



Ovate, thin, smooth, shining, transparent, umbilicated ; Avhorls 

 of rapid growth, ventricose, only five: mouth ovate, almost equal 

 to the spire above it ; pillar lip much elongated, and, as well as 

 the outer one, much arched, very narrowly reflected ; fold small, 

 but distinct. 



Plate XCIV. fig. 6. 



OJontomia nitida, Ai-DER, Ann. Nat, Hist. vol. xiii. p. 32G, pi. 8, f . 5 ; Catal. 

 Moll. Northumb. and Durh. p. 52. — Jeffreys, Ann. Nat. 

 Hist, new ser. vol. ii. p. S.'JT. 



We have only seen a single example (that from which 

 the sjiecies was originally constituted) of this rare little 

 shell, whose characteristics, though not striking, are suf- 

 ficiently dissimilar to those of its allied congeners, to render 

 its recognition an easy task. Its form is ovate-conical, and 

 it is thin, shining, semitransparent, smooth, and white. 

 The increase of the volutions in both directions is rapid ; 

 the spire, which is composed of barely four turns, quickly 

 tapering to a very blunt apex. The whorls are tumid and 

 but moderately high ; the principal ones, instead of shelving- 

 above, project there abruptly in an obtusely scalar fashion ; 

 they, likewise, incline a little inward at their bases ; hence 

 the slightly oblique line of division is peculiarly well pro- 

 nounced. The basal declination of the body-whorl, whose 

 periphery is not at all angulated, is well and gradually 

 rounded. The mouth occupies three-sevenths of the entire 

 length, is exactly ovate, and not angularly contracted at 

 its upper end ; the throat is quite smooth. The outer lip 

 is continuously arcuated, and projects very decidedly at the 

 anterior extremity. The pillar-lip is peculiarly elongated, 

 filling two-thirds of the length of the inner lip ; it is very 



