OVULA, 



The Ovula hirostris ( Bulla birostris, auctor.) is of an 

 oblong shape, its superior canal is rather elongated and 

 pointed at the apex; the upper part of its aperture is 

 narrow, and the lower part proportionably wider than in 

 other species : its inferior canal appears also to be pointed. 



The Ovula gibbosa ( Bulla gibbosa, Linn J is of an 

 oblong shape, it has near the middle of the back a dis- 

 tinct, obtuse, transverse ridge, and its canals are extremely 

 short. 



A fifth species, of which we have given a representa- 

 tion, is the Ovula verrucosa^ ( Bulla verrucosa^ Linn.) this 

 is perhaps the most remarkable; it is oblong, the back is 

 elevated into an obtuse ridge, and finely striated; its outer 

 lip is distinctly and regularly denticulated, but its chief 

 peculiarity consists in having an orbicular shelly tubercle 

 on the outer part at each extremity, exactly opposite to the 

 canals; from these it has received its specific name. 



Seven other recent species of this Genus are described 

 Lamarck in the 16th vol. of the Ann. du Museum, but 

 as it would be going too far beyond our immediate object 

 to describe all the species, we shall be content with men- 

 tioning particularly the O. costellata of Lam. which is the 

 same as the Bulla imperialis of English Authors ; a very 

 pretty shell, and deservedly valued by Collectors. ' 



Two fossil species are also noticed by Lamarck, both 

 from one of more recent formations, and found at Plaisance. 



The animal of this Genus is unknown to us, but as all 

 the species when they have arrived at their adult state are 

 more or less covered with a shining enamel-like shelly coat 

 evidently deposited after the formation of the outer invo- 

 lute lip, we have reason to believe that its bipartite mantle 

 IS capable of extension at pleasure, over almost the whole 

 of the outer part of the shell, nearly in the same manner as 

 in Ciyproia. The knowledge of the animal may, at some 

 future period, evince the propriety of separating- the shells 

 here included in Ovula, into several genera; until that pe- 

 riod arrive, we think it more for the interest of Science to 

 keep them united ; and the more so, as we are quite cer- 

 tain, from the characters of the shells, that there must be 

 considerable resemblance m those characters and habits by 

 which the animals will be distinguished. 



We cannot consider the Eiiglish Bulla paiula to be an 

 Ovula. 



