348 MOLLUSCA. 



Arera, Muller. 



The branchiae covered, as in the preceding genera, but their tentacula 

 are so shortened, widened and separated, that they seem to be totally 

 wanting, or rather to form a large, fleshy, and nearly rectangular 

 shield, under which are the eyes. Independently of this, the herma- 

 phroditism of these animals, the position of their genital organs, the 

 complication and armature of their sjomach, and the purple liquid 

 effused by several of their species, approximate them to the Aplysise. 

 The shell, of such as have any, is more or less convoluted, but with 

 little obliquity, and is without a projecting spire, emargination, or 

 canal; the columella, projecting convexly, gives a crescent-like figure 

 to the aperture, the part opposite to the spire being always the 

 broadest and most rounded. 



M. de Lamarck names those in which the shell is concealed in 

 the thickness of the mantle, Bull^ea. It has but very few whorls, 

 and the animal is much too large to be drawn into it. 



Bullxa aperta, Lam.; Bulla aperta and Lobaria quadriloba, 

 Gin.; Phyline qitadripartita, Ascan.; Mull., Zool. Dan., Ill, pi. 

 cij Blanc, Conch. Min. Not., pi. xi; Cuv., Ann. du Mus. t. I, 

 pi. xii, 6(1). The animal is whitish, and about an inch long; 

 the fleshy shield, formed by the vestiges of its tentacula, the 

 lateral swellings of its foot, and the mantle occupied by the 

 shell, seem to divide its upper surface into four lobes. Its thin, 

 white, semi-diaphanous shell, is nearly all aperture, and its giz- 

 zard is armed with three very thick rhomboidal pieces of bone. 

 It is found in almost every sea, where it lives on oozy bottoms. 

 M. de Lamarck leaves the name of Bulla(2) to those species 

 whose shell, merely covered with a slight epidermis, is large enough 

 to shelter the animal. It is somewhat more convoluted than in 

 Bullaea. 



Bulla lignaria^ L.; Martini, I, xxi, 194, 95; Cuv., Ann. du 

 Mus., XVI, 1; Pol. Test. Neap., Ill, pi. xlvi. The oblong shell. 



(1) The Sormet, Adans., Senegal, pi. i, f. 1, is a species closely allied to Bul- 

 laca; but I cannot establish a genus, or even a species, upon so imperfect a docu- 

 ment. 



(2) The genus Bulla, Lin., not only comprised the Aherse, but also the £^uri- 

 cuhe, Jgatinae, Physx, Ovulse and Tcrebella, animals between which there is much 

 difference. JBrugieres commenced the work of reformation by separating the 

 AgatinsE and the Auriculs, which he united to the Lymnei in the genus Bulimus; 

 M. de Lamavck finished it by creating all the genera we have just named. 



