BULLA. 531 



DiLLW. Recent Shells, vol. i. p. 479. — Woud, Index Testae, 

 pi. 18, f. 17.— Blainv. Man. Malacol. pi. 46, f. 1. 

 Bulla ampulla (not of Linn.), Penn. Brit. Zool. ed. 4, vol. iv. p. 116 ? 

 „ uavicula, Da Costa, Brit. Conch, p. 28, pi. 1, f. 10. 

 „ cornea. Lam, Anim. s. Vert. (ed. Desh.) vol. vii. p. 67'2. — Deles. Rec. 



Coq. Lam. pi. 27, f. 7. 

 „ {Haminea) liydatis, A. Adams, Sow. Thesaur. Conch, vol. ii. p. 578, 

 pi. 124, f. 81,82. 



As some little doubt exists whether the small oval 

 Mediterrauean examples,* with a more indented crown, 

 be or be not identical with our ordinary rounded and 

 tumid form, we have so framed our synonymy as solely to 

 apply (the reference to Linnaeus excepted) to the latter, 

 which, as Da Costa named anew, whilst acknowledging it 

 to be the liydatis of Linnaeus, must take the name of cornea^ 

 if regarded as specifically distinct. Both forms, however, 

 appear to exist in the Mediterranean, and if we may trust 

 to the indigenousness of certain examples in the hands of 

 collectors, both are likewise taken upon our own coast. 



The shell, which is very thin and semitransparent, has a 

 rounded ovate contour, and is neither contracted nor trun- 

 cated posteriorly: it is covered by a yellov/ish or ferruginous 

 skin (that is shining and pellucid in the young, but is occa- 

 sionally opaque and dull in the more aged individuals), 

 beneath which the surface, which is most densely encircled 

 throughout with most minute and slightly undulated spiral 

 striulse, is of an uniform whitish or pale yellowish cast. 

 The body, which is ventricose or even tumid, and whose 

 slopes are well rounded at both ends, is not surmounted by 

 any spire ; its crown displays a slight umbilical indenta- 

 tion, but no true perforation. The curved and somewhat 

 capacious aperture is moderately open throughout, but 

 enlarges decidedly anteriorly, owing to the great incurv- 



* Delle Chiaje in Poll, Test. Sicil. vol. iii. pt. 2, p. JO", pi. 4(), i', 28. 



