OVULA 



in which we have included five species, all agreeing in 

 certain characters, which we have considered as the generic 

 characters : we shall first detail these, and then enter a 

 little more particularly into the peculiar distinctive charac- 

 ters of the five species we have drawn. In their general 

 form the shells ojP this Genus are more or less ovate, and 

 gibbous, their spires are always hidden ; for their convolu-* 

 Hon is horizontal, the whorls never descending as they 

 increase, but always preserving the same plane. Their 

 aperture is longitudinal, elongated, narrow at its upper 

 part, and more expanded below ; both the superior and 

 inferior extremities are notched, and each of them produced 

 into a canal: the inner lip is smooth, without teeth or any 

 kind of denticulation ; and the outer //p is thickened and 

 mostly turned inwards. The various length of the canals 

 in the several species, added to the presence or absence of 

 denticulation on the inner part of the outer lip , are the 

 characters upon which Montfort has founded the distinctions 

 between his four genera. 



Several species of the Genus Ovula are known, one of 

 the n[iost common is the Ovula oviformis of Lam, : the Bulla 

 Ovum of Linn, it is an egg-shaped shell, very white and 

 smooth on the outside, its canals are both short, and the 

 inner part of the outer lip is furnished with blunt denticu- 

 lations, and when full grown it is coloured within of a more 

 or less dark and rich brown : in its young state its outer 

 lip is not involute nor denticulated, the outside is covered 

 with fine transverse striae, and it is colourless. We see no 

 reason for altering its specific denomination, and therefore 

 with Montfort have called it Ovula Ovum. 



The Ovula Volva ( Bulla Volva Linn.) is remarkable 

 for the great length of the canals — of these the upper one 

 is rather the longer, and the lower one is turned a little 

 backward ; the outer lip in this species is considerably 

 thickened, but it is not so perfectly involute as in the other 

 species. The outside of the body of this shell, when in 

 good condition, is covered with transverse impressed strias ; 

 these diverge as they approach the lip, and become oblique 

 towards the canals on which they gradually increase so 

 much in breadth as rather to form the spaces between 

 oblique raised lines, than to deserve the appellation of 

 impressed sirice. This is the JVeavers'' Shuttle of the Eng- 

 lish Collectors; when perfect and fine it is held in consider- 

 able estimation by them. 



