48 MOLLUSCA. 



pieces of bone. It is found in almost every sea, where it lives on 

 oozy bottoms. 



M. de Lamarck leaves the name of BULLA*, 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 Wafer.) The 

 oblong shell with its concealed spire and ample aperture, very 

 wide anteriorly, resembles a loosely rolled lamina, streaked in 

 the direction of its whorls. The stomach of the animal is armed 

 with two large semi-oval osseous pieces, and with a small com- 

 pressed onef. 



Bulla ampulla. L,; Martini, I, xxii, 20, 204; Cuv., Ann. du 

 Mus., XVI, 1. (The Nutmeg). The shell oval, thick, clouded 

 with grey and brown ; the stomach furnished with three black, 

 very convex, rhomboidal pieces. 



Bulla Hydatis, L, ; Chemn. IX, cxviii, 1019 ; Cuv., Ann. du 

 Mus., XVI, I. (The Water Drop.) Shell round, thin, and semi- 

 diaphanous ; the last whorl, and consequently the aperture, 

 higher than the spire ; three small scutelliform pieces in the 

 gizzardj. 



We reserve the name of AKERA, properly so called, DORIDIUM, 

 Mech., LOB ARIA, Blainv., for those species which have no shell what- 

 ever, or only a vestige of one behind, although their mantle has its 

 external form. 



A small species, Bulla carnosa, Cuv., Ann. du Mus., XVI, 1 ; 

 Meek., Anat. Compar., II, vii, 1, 3; Blainv. Malac., pi. xlv, f. 

 3, is found in the Mediterranean. The only armature of the 

 stomach is the mantle ; its fleshy oesophagus is extremely thick. 



A tuberculous species, Doridium Meckelii, Delle Chiaie, Me- 

 mor.,pl. x, f. 1 5, inhabits the same sea. The 



GASTROPTERON, Meckel. 



Appear to be Akerse, the margin of whose foot is extended into 

 broad wings, used in natation, which they effect on their back. It 

 has no shell, nor has the stomach any armature ; a slight fold of skin 

 is the only vestige of branchial operculum that is perceptible. 



* The genus Bulla, Lin., not only comprised the Akerez, but also the Auricula, 

 Agaiintf, Physa, Ovula and Terebella, animals between which there is much difference. 

 Bntgieres commenced the work of reformation by separating the Agatinee and the 

 Auriculae, which he united to the Lymnei in the genus Bulimus ; M. de Lamarck 

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



f Gioeni having observed this stomach separate from the animal, mistook it for 

 a shell, and made a genus of it, to which he gave his own name (The Tricla of 

 Retzius, Char, Brug.). Gioeni even went so far as to describe its pretended habits. 

 Draparnaud was the first who perceived this mixture of error and fraud. 



J Add, Bulla naucum ; Bulla physis. Muller describes smaller ones, such as the 

 Akera bullata, Zool. Dan., LXXI, or Bulla akera, Gin. 



